Dictionary of video and television technology

The book is a valuable reference for engineers working in the fields of analog and digital video, broadcast personnel, tech- nicians, or anyone charged with the task of understanding, us

Dictionary of Video and Television Technology

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Copyright © 2002, Elsevier Science (USA) All rights reserved

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Dictionary of Video and Television Technology

Keith Jack Vladimir Tsatsulin

A m s t e r d a m B o s t o n L o n d o n N e w Yo r k O x f o r d P a r i s

An impr int of Elsevier Science

[This is a blank page.]

Preface vii

About the Authors ix

# 1

A 3

B 22

C 39

D 75

E 100

F 113

G 129

H 135

I 146

J 159

K 161

L 164

M 176

N 193

O 199

P 205

Q 224

R 227

S 239

T 271

U 289

V 292

W 311

X 316

Y 317

Z 319

APPENDIX A: Associations 321

APPENDIX B: Standards Organizations 325

Just a few short years ago, the applications for video were fairly confined— analog broadcast and cable television, analog VCRs, analog settop boxes with limited functionality, and simple analog video capture for PCs Since that time, a tremendous and rapid conversion to digital video has taken place, with consequent changes in broadcast standards and technologies.

“Convergence” is the buzzword that has come to mean this rapid coming together of various technologies that were previously unrelated Today we have:

• DVD and SuperVCD players and recorders, with entire movies being stored on one disc, with newer designs supporting progressive scan capability for even higher video quality.

• Digital VCRs and camcorders, that store digital audio and video on tape.

• Digital settop boxes, which interface the television to the digital cable, satellite, or broadcast system Many also now support interactivity, datacasting, sophisticated graphics, and internet access.

• Digital televisions, which receive and display digital TV broadcasts, either via cable, satellite, or over-the-air Both standard-definition (SDTV) and high-definition (HDTV) versions are available.

• Game consoles, with high-definition graphics and powerful ing, and with the newer systems supporting DVD playback and internet access.

process-• Video editing on the PC, using real-time MPEG decoding, fast MPEG encoding, and other powerful techniques.

• Digital transmission of content for broadcast, cable and satellite tems, with the conversion to HDTV underway.

sys-This is a complex and ever-changing field and there is a need for a ence that documents the evolving terminology, standards, and acronyms.

refer-The Dictionary of Video and Television Technology contains the most

up-to-date terms and their usage The book is a valuable reference for engineers working in the fields of analog and digital video, broadcast personnel, tech- nicians, or anyone charged with the task of understanding, using, or implementing video and television signals We hope this companion vol-

ume to the popular Video Demystified, 3rd Edition proves just as valuable to

those creating and working with the converging technologies of the 21st

century.

ABOUT THE AUTHORS

Keith Jack has architected and introduced to market over 25 multimedia

ICs for the PC and consumer markets Currently director of product keting for Sigma Designs, Inc., he is working on next-generation digital video and audio solutions He has a BSEE from Tri-State University in Angola, Indiana, and holds two patents for video processing.

mar-Vladimir Tsatsulin is a retired military officer with an electronics

engineer-ing degree from MVIZRU Military Academy Followengineer-ing his retirement from the military, he worked as a TV technology professor at “Elektrons” state company in Riga, Latvia and later was a member of the expert group that developed a TV and PC database for the Invention Machine Co Today Tsatsulin is a technical writer and translator for the Belorussian State Univer-

sity of Informatics and Electronics in Minsk, Belarus He is co-author of The

English-Russian Dictionary on Television and Audio/Video Equipment, a

stan-dard reference now in its third edition.

[This is a blank page.]

0h A reference time moment at the mid-level crossing

point of the leading edge of the line sync pulse This

is the default timing reference in the TV

environ-ment (as opposed to the active line start which is

commonly used in computing environments) Syn.:

line datum; line start [moment]; time datum

0v A reference time moment given by the line datum

coincident with the beginning of the first

equaliz-ing pulse (525-line standard) or with the beginnequaliz-ing

of the first broad pulse in the vertical sync group

(625-line and 1125-line standards) Commonly

ac-cepted as a timing reference point for color framing

and SCH determination in 625-line standard Syn.:

frame datum

1.78:1 16:9 ratio for “wide-screen” TV.

10-bit The generic description for equipment having a

data path 10 bits wide Such a path can represent

data having up to 1024 different values (four times

that of an 8-bit system)

100% [color] bars 1 In PAL/SECAM countries and in

Japan: color bars with the nomenclature 100/0/100/0

2 In the USA and other NTSC countries: color bars

with the nomenclature 100/7.5/100/7.5

12-12-12 rule The maximum number of stations that

can be owned by one company: 12 TV stations, 12

AM radio stations, and 12 FM radio stations This

rule of the FCC replaces the longtime limitation of

7-7-7

12-14 truck Ku-track, named for the GHz range.

12-14 unit Ku-track.

1080i Number of active vertical scanning lines in

inter-laced scan format specified by HDTV standard

adopted by the FCC See Interlaced scanning.

1,300-nm optical-wavelength transmission window

An optical wavelength frequently used for cable-TV

trunk and other multi-km fiber-optic systems

16-VSB system Zenith’s 16-level digital transmission

system, using vestigial sideband modulation

tech-nology Can send two digital HDTV MPEG-2 signals

on a single 6-MHz cable channel, doubling the

num-ber of HDTV signals on a cable channel Alternately,

it can be used to deliver as many as 24 SDTV

MPEG-2 channels, or a mix of HDTV and SDTV channels

With a data rate of 38.8 megabits/s, it has twice the

data rate of 8-VSB Although designed for digital

cable, many digital cable systems continue to useQAM modulation technology

2-D Two-dimensional.

(2+3)D mode A mixture mode in which both the

2D-image and the 3D-image are displayed as mixed

2.5D effect A digital video effect similar to a 2D effect

but with the appearance of three dimensions E.g.,

a picture can be distorted and put on the surface of

a disk to give the illusion of being put on a sphere Ifthis disk is rotated 90 degrees about its x-axis it will

be seen to be a single line, providing its 2D nature

A true 3D effect may be rotated and viewed aboutany axis and still maintain an appropriate shape

2D effect A digital video effect where picture

trans-formations and manipulations are restrained within

an arbitrary plane surface

2H Sync pulse with period of two lines, the rising edge

of which marks the start of a line with positivepolarity of V component in a PAL chrominance sig-nal or the start of a Dr line in Dr/Db sequence in aSECAM chrominance signal Syn.: 7.8 kHz; Dr/Dbswitch; PAL switch; PAL switching signal; SECAMswitch

3C Computer, communication, consumer Color

videophone is an example of a 3C integrated product

3-D Also 3D Three-dimensional.

3-D display technology A technique, developed by

Sanyo Electric Co Ltd of Osaka, that does not quire special viewing glasses Instead, a proprietaryimage splitter separates images into right-side andleft-side elements The splitter works in conjunctionwith a conventional LCD to produce the image Aspecial algorithm and digital-signal processing canproduce real-time 3-D images from ordinary 2-D sig-nals such as conventional TV and video programming

re-3:2 pull-down A method used to map film (24 fps)

onto 480-line TV (30 fps), in which one film frameoccupies three TV fields, the next two, and so forth.Since the two fields of alternate TV frames are fromdifferent film frames, operations such as rotoscopingare not possible, and editing must be done care-fully Advanced equipment can unravel the 3:2sequence to allow frame-by-frame treatment

3/4-inch U (EIAJ) Video Recording Format The first

mass-produced and practical videocassette format

and machine to be used in the US Introduced by

Sony in 1971, this videotape format uses the trade

name U-matic (shortened to just U), which has

be-come synonymous with the machine It was

en-dorsed as the standard for 3/4" tape recording by

the Electronic Industry Association of Japan (EIAJ)

4:1:1 Y’CbCr Means that for every four horizontal Y’

samples, there is one sample each of Cb and Cr

4:2:0 Y’CbCr Means that for every block of 2 x 2 Y’

samples, there is one sample each of Cb and Cr

There are three variations of 4:2:0 YCbCr, with the

difference being the position of Cb and Cr sampling

relative to Y

4:2:2 Also CCIR 601, ITU-R BT.601 The most

com-monly accepted standard for component digital

video The active picture area of the luminance Y’

component is 720 pixels horizontally by 480 or 576

lines vertically (per frame) Each of the color

differ-ence signals, Cb and Cr, are sub-sampled

horizon-tally so that, per frame, they each have 360 pixels

horizontally by 480 or 576 lines vertically At 8 bits

per pixel, the total active picture rate is 166 Mbps

The full bit rate including line and field blanking

periods is 216 Mbps Likewise for 10 bits per pixel,

the active picture data rate is 207 Mbps with the

full bit rate at 270 Mbps This is the standard for

digital studio equipment; the terms “4:2:2” and

“601” are often used synonymously (but

techni-cally incorrectly)

4:2:2 Y’CbCr Means that for every two horizontal Y’

samples, there is one sample each of Cb and Cr

4:4:4 Y’CbCr Means that for every Y’ sample, there is

one sample each of Cb and Cr

4fsc Four times the frequency of the NTSC or PAL color

subcarrier Also the sampling rate of a D2 digital

video signal with respect to the subcarrier frequency

of an NTSC or PAL analog video signal

5.1 A type of surround sound using six audio

chan-nels: left, center, right, left rear (or side) surround,

right rear (or side) surround, and a subwoofer,

con-sidered the “.1” since it is bandwidth-limited

601 See 4:2:2.

7-7-7 rule An FCC restriction that formerly limited

own-ership by one company to a maximum of seven TV

stations (of which only five could be VHF), seven

AM radio stations, and seven FM radio stations; now12-12-12

7.8 kHz See 2H.

780p Number of active vertical scanning lines in

pro-gressive scan format specified by HDTV standard

adopted by the FCC See Progressive scanning.

8mm Hi-Fi High sound quality built into the 8mm video

recording format This format was originally designed

to automatically incorporate AFM hi-fi recording inall 8mm camcorders and VCRs Unlike standard VCRsthat place the separate audio track longitudinally

on the tape, 8mm AFM units “write” the audio track

on the tape diagonally along with the video mation The high quality sound, however, is restricted

infor-to one monophonic track, thereby not necessarilyproducing stereo Some 8mm units are equippedwith Pulse Code Modulation, a digital audio record-ing process that can produce stereo audio

8mm/VHS, VCR; Sony A dual-deck VCR that can edit

from 8mm to VHS and vice versa Both decks havehigh-end features such as stereo audio and the ca-pability of accommodating high-band recordings(Hi8 and S-VHS), but in standard resolution only In-cluded are several editing features, including jog/shuttle controls

8mm video A mini-video camcorder format that uses

a compact cassette (60-, 90- or 120-minute lengths)and is capable of producing hi-fi audio Flying eraseheads provide smooth edits and clean scene transi-tions The video quality of the 8mm format equalsthat of VHS in many respects and surpasses it, al-though only slightly, in color reproduction In addi-tion, its built-in hi-fi audio capability offers superiorsound to competing formats However, 8mm video

is not compatible with most home VCRs Some els have added advanced features, such as automaticfocus, glitch-free editing and the capability of su-perimposing time and date upon an image Othercompetitive formats include Hi8, S-VHS, S-VHS-C,VHS-C

mod-8-pin connector A type of jack commonly used for the

VTR-to-monitor connection; provides a full set of dio and video connections—one ground and one leadeach for audio-in, audio-out, video-in, and video-out

au-8-VSB See vestigial sideband.

4:1:1 Y’CbCr

ABC Commonly refers to the American Broadcasting

Corporation or the Australian Broadcasting ration May also be an abbreviation for automaticbrightness control

Corpo-aberration In CRT displays, a distortion of an image

caused by failure of the electron beam to focus allpoints accurately on the screen

ABL Abbreviation for automatic brightness limiter above the line A budget category that includes the

artistic or creative elements, primarily nontechnicalpersonnel and activities

abstract set A set, such as on a TV news program,

that has a neutral background

AC adapter An external device for equipment that

converts alternating current (AC) power into directcurrent (DC) power

AC coupled AC coupling passes a signal through a

capacitor to remove any DC offset, or the overallvoltage level that the video signal “rides” on Oneway to find the signal is to remove the DC offset by

AC coupling, and then do DC restoration to add aknown DC offset (one that we selected) Anotherreason AC coupling is important is that it can re-move large (and harmful) DC offsets

AC hum A low-pitched sound (50 or 60 Hz) heard

whenever AC power is converted into sound It isusually the result of ground loops or inadequateshielding of cables

AC interlock A safety function on equipment that turns

off power when the back of the device is opened

AC transmission See Alternating-current transmission.

AC’97, AC’98 These are definitions by Intel for the

audio I/O implementation for PCs Two chips aredefined: an analog audio I/O chip and a digital con-troller chip The digital chip will eventually be re-placed by a software solution The goal is to increasethe audio performance of PCs and lower cost

AC-3 Original name for Dolby® Digital Also, the

ver-sion of Dolby compressed audio used in some movietheaters for surround sound

ACATS Abbreviation for Advisory Committee on

Advanced Television Service

ACC Abbreviation for automatic color control.

accelerating anode See Electron gun.

accelerating electrode An electrode that accelerates

A The cable TV midband channel occupying 120-126

MHz May also refer to an advertising rate for

com-mercials (see AAA rate).

A&E Abbreviation for Arts and Entertainment cable

channel

A.F Abbreviation for audio frequency.

A/D Short for analog-to-digital converter.

A/D converter Short for analog-to-digital converter.

A/PAL An early version of PAL used in Ireland and the

United Kingdom Characteristics were 405 lines per

frame, 50 fields per second, 2:1 interlaced

A-1 The cable TV midband channel occupying

108-114 MHz

A-2 The cable TV midband channel occupying

114-120 MHz May also refer to Antenne-2, or the

second French state broadcast TV network

AA The cable TV hyperband channel occupying

300-306 MHz May also refer to an advertising rate

for commercials (see AAA rate).

AAA rate The most expensive advertising rate for

ra-dio and TV commercials AA is the next lower rate,

followed by the A rate, and finally the B rate (the

lowest rate)

A-B color frame code Another name for color frame

code

A-B mix A transition where one video source (A) fades

out while another video source (B) fades in The

amount of each source used to generate the result

is determined by the relative position of a mixer fader

arm When the fader arm is all the way at the source

A side, then only video source A appears at the

output Also means cross-fade or mix

A-B roll A video editing system where two or more

sources are used, in conjunction with a video mixer,

to create dissolves and other transitions between

the different sources

A-B roll editing An editing procedure using two

syn-chronized sources of the same program material

A-B switch A device that inputs two video sources (A

and B), and outputs either A or B Since it doesn’t

affect the signal quality, it is also called a passive

switcher

A-B test A direct comparison of sound and/or picture

quality of two sources, or devices, by playing one,

then the other

the electrons of an electron beam See also Electron

gun.

acceleration voltage A voltage that produces an

ac-celeration of a beam of charged particles

accentuation Another name for pre-emphasis.

accentuator Another name for a circuit that provides

pre-emphasis

access In videotex, the number of frames requested

by a user

access time In video, the amount of time it takes to

reach the desired point of a program

ACE head On newer VCRs, the control-track and

au-dio heads are combined into one unit This head is

often referred to as the ACE head, for Audio,

Con-trol, and audio Erase

achromatic Without color or varying brightness

information May also refer to being capable of

trans-mitting light without breaking it up into its

constitu-ent colors Also see Monochromatic.

achromatic color A shade of gray Also see Variables

of perceived color.

achromatic lens A lens corrected for chromatic

aber-ration In its simplest form, it consists of a pair of

lenses, designed so that the dispersion produced by

one lens (being divergent) corrects the dispersion

produced by the other (being convergent) Usually,

a convex lens of crown glass and a concave lens of

flint glass are used The combination brings all

col-ors closer to the same focal point

achromatic locus The area on the chromaticity

dia-gram that contains all points representing

accept-able reference white standards Also called the

achromatic region

achromatic point A point on the chromaticity

dia-gram representing an acceptable reference white

standard

achromatic region See Achromatic locus.

achromatic stimulus A visual stimulus that gives the

sensation of white light and thus has no color

ACK Abbreviation for automatic color killer.

acoustic delay line A delay line used to delay sound.

It may be mechanical or electronic

acoustic feedback This may occur when the input to

a system (such as a microphone) receives sound from

the output of the system (such as a speaker),

form-ing an uncontrolled closed loop It usually results in

a high-pitched squeal

acoustic holography Using a single-frequency sound

wave to produce a 3D image of an object It is

usu-ally viewed on a CRT display

acoustic wave A wave that is transmitted through a

solid, liquid, or gaseous material as a result of

vibra-tions of the particles Also called a sound wave

acoustic wave device A device used in signal

pro-cessing that transfers acoustic waves on a substrate,

enabling a wide variety of processing functions to

be performed Delay lines, attenuators, phase

shifters, etc may be implemented

acoustics The reverberation of sound, or lack of it, in

a room Acoustics can affect the results of the audiorecording Some parts of a room have “dead” spotswhile others are more “lively.” The built-in micro-phone of a video camera operates better in deadareas; hiss and noise occur in live portions of a room

ACS Abbreviation for alternate channel selectivity.

action line See Line.

action shot See Moving shot.

action track A digital video effect where fast-moving

objects appear to remain on-screen This effect quires motion detection to isolate the moving ob-jects so that they may be frozen and accumulatedinto a single image The technique was developedfor sports action replay analysis Also called imagetrail-freeze

re-active filter A filter that requires power to operate.

Also refers to a filter designed to reject noise andripple that may otherwise be transmitted to a TVtuner

active image The visual portion of a video signal.

active image area See Active picture area active interval The portion of an active line that con-

tains video information Also see Trace interval and

Sawtooth.

active lines The scan lines of a video signal that

con-tain picture information Most, if not all, of theselines are visible on the display Scan lines that do notcontain video information are usually said to be inthe vertical blanking interval

active material A fluorescent material used in CRT

displays

active mixer An audio mixer that compensates for

signal losses Some active mixers can also modifythe audio signal by compressing it, adding echo, ormodifying a specific frequency range

active part The portion of a video scan line that

car-ries picture information Also called analog activepart

active picture area The useful portion of a video

dis-play

active pixel region The area of the display used for

the actual display of information There may be avisible region not used to display information, calledthe border region

active position The position on a display where

sub-sequent actions will occur

active satellite See Communications satellite active scan line See Active lines.

active signal correction A common name for the

fuzzy logic used in some video equipment See ASC.

active video The part of the video waveform that

contains picture information Most of the activevideo, if not all of it, is visible on the display

active-matrix LCD Active matrix is a technique for

making color LCD displays, by using transistors tomake up each of the pixels The most common type

of active matrix LCD is based on a technology known

acceleration voltage

as TFT The two terms, active matrix and TFT, are

often used interchangeably

actuator In general, a device, under the control of an

electrical signal, which carries out a mechanical

ac-tion It may also refer to the VCR device that causes

the video head to be moved to the videotape track

In satellite TV, it controls the movement of the

satel-lite dish so that it receives the strongest signal

ACTV Abbreviation for Advanced Compatible

Television

ACTV-1 In 1988, a proposed system described by

Isnardy had undergone computer simulation at the

David Sarnoff Research Center The system was

named ACTV-1, for “Advanced Compatible TV, First

System.” It was intended to provide a 16:9

wide-screen picture, while being compatible with

stan-dard NTSC receivers, and use the stanstan-dard 6-MHz

NTSC channel To accomplish this, a second

subcar-rier was added to the NTSC signal This second

sub-carrier was a 395th multiple of one-half the line

fre-quency, or about 3.1075171 MHz An additional

“helper signal,” quadrature modulated with the

pic-ture carrier, was used to improve the vertical

resolu-tion The ACTV-1 receiver was to be a 16:9

wide-screen 525-line progressive TV

ACTV-2 This proposed system used two 6-MHz NTSC

channels, with the ACTV-1 system being used for

one of the channels The ACTV-2 system was an

extension of the ACTV-1 system The ACTV-2

receiver was to be a 16:9, 1050-line interlaced TV

adaptation The dynamic change of the type of audio

or video processing performed, dependent on the

sound or picture content

adapter A device that makes electrical and

mechani-cal connections between equipment not originally

intended to be used together

adaptive comb decoder A NTSC/PAL video decoder

that uses an adaptive comb filter.

adaptive comb filter A filter that performs luminance

(Y) and chrominance (C) separation based on the

picture content The frequency responses of the Y

and C filters look like the teeth on a comb, hence

the name comb filter

adaptive control Processing that varies automatically

to generate the desired results regardless of the

in-put The automatic gain control (AGC) is an example

of an adaptive control: the gain of the amplifier

var-ies automatically to generate a constant output level,

regardless of the input level

adaptive range coding A process that condenses the

entire NTSC or PAL video bandwidth into a digital

signal that can be recorded on tape The technique

requires the use of high-grade metal-particle tape

adaptive transform/sub-band coding See Zenith

Spectrum-Compatible HDTV System.

adaptive transformation A video compression

tech-nique The amount of information that must be

transmitted for a particular portion of the image is

proportional to the fineness of detail in that tion A portion of the picture with little detail can

por-be transmitted with very few bits, and this providesextra time for transmitting portions with high de-tail A buffer is used to restore the original spatio-temporal relationship If the entire picture has highdetail, the buffer may become overloaded, so therate of information transfer is reduced by reducinghigh-frequency details This, of course, reduces theimage quality by introducing artifacts

ADC, A/D Abbreviation for analog-to-digital converter Add-A-Vision A combined film and TV camera sys-

tem based on the Mitchell BNC but of British sign A variant of Add-A-Vision known as EFS (Elec-tronic Filming System) is basically similar, but em-ploys the Mitchell Mark 2 camera

de-additive color system Color based on the addition

of light For video, the three primary colors are red,green, and blue These may be added together invarying amounts to generate any other color Colorprinting and film use the subtractive color system

additive primaries Three colors from which all other

colors can be generated by adding some mixture ofthem together

add-on recording Also called transition editing

re-cording Most VCRs allow pause during recording,but due to timing problems, there is usually a distur-bance of the picture during playback at the placewhere the pause was used To eliminate this distur-bance, transition editing recording backs up the tapefor about 2.2 seconds during pause recording Whenthe pause is released, the deck will play back forabout 1.2 seconds while aligning the control timingalready on the videotape to the desired timing Af-ter about 1.2 seconds, the deck switches to therecord mode, with the overall effect of there being

no artifacts during playback

address search Also known as VASS or VHS Address

Search System, it is a VCR feature that permits theuser to assign a number to each index stop by mark-ing it magnetically or electronically Most VCRs useone or more search methods to find a specific scene

on a videotape These machines automatically place

an electronic mark on the tape each time the Recordbutton is activated, thereby marking the beginning

of every program recorded Other features allow forspecific scenes within a program to be marked

address track In VCRs, a path for laying down a

spe-cific code number for each frame of video on thetape This code consists of a time so that, for ex-ample, 00:27:14:03 would be read as 00 hours, 27minutes, 14 seconds, and 3 frames

addressability The ability of a cable or satellite TV

provider to control a set-top box in a subscriber’shome If communication from the set-top box tothe provider is also possible, it is called a two-waysystem Otherwise, it is called a one-way system

addressable box A set-top box used by cable and

addressable box

satellite TV providers that supports addressability It

connects between the cable outlet (or satellite dish)

and the TV, allowing viewers to order and receive

pay-per-view programs and subscription channels

addressable converter See Addressable box.

addressable decoder See Addressable box.

addressable programming A cable or satellite TV

provider may enable or disable a specific program

from being decoded and displayed by a specific

ad-dressable box For example, a viewer orders a

pay-per-view movie They call a phone number; a

com-puter answers and confirms the request The

pro-vider then sends a coded message, which is received

by the viewer’s addressable set-top box The

mes-sage temporarily enables that particular set-top box

to descramble the channel, offering the desired

pro-gram

addressable set-top box See Addressable box.

addressable system A cable or satellite TV system

that supports addressable programming

adjacent channel A channel that is immediately next

to another channel in frequency For example, NTSC

channels 5 and 6 are adjacent However, channels 4

and 5 are not since they are separated by non-TV

signals

adjacent sound carrier The RF carrier that conveys

the audio information for the channel immediately

below the desired channel

adjacent video carrier The RF carrier that conveys

the video information for the channel immediately

above the desired channel

adjacent-channel interference Interference caused

by an adjacent channel

adjacent-channel selectivity The ability of a receiver

to reject signals on adjacent channels

adjustment switches For a display, the controls for

horizontal synchronization, vertical synchronization,

luminance, hue, contrast, etc

ADO Abbreviation for Ampex Digital Optics by Ampex

Corporation This is a video special effects device

for creating effects such as flips and twists

ADP Abbreviation for automatic data processing.

ADSL Asymmetric Digital Subscriber Line, a

technol-ogy that converts existing copper telephone lines

into access paths for multimedia and high-speed

data communications while maintaining the

regu-lar phone voice services The ANSI T1 committee has

standardized Discrete Multi-Tone (DMT) as the line

code to be used in ADSL See DMT.

ADTV Abbreviation for Advanced Digital Television.

advance ratings When an audience-survey company

provides a preview (by telephone) to a client of the

ratings of a radio or TV program or station

Advanced Compatible Television Several techniques

were developed to transmit additional information

within the NTSC and PAL video signal Conventional

TVs would ignore the additional information, and

display the usual picture Advanced TVs would use

the additional information to display an improvedpicture, usually with a 16:9 aspect ratio None of

the techniques were popular, although PALplus was

introduced in Europe

Advanced Digital Television (ADTV) A proposed fully

digital HDTV system, since replaced by the ATSCHDTV standard; Advanced Television Research Con-sortium (Thomson Consumer Electronics, Philips,NBC, David Sarnoff Research Center, CompressionLaboratories Inc.) The baseband input was 1050lines, 2:1 interlaced, and 59.94 fields/s Source cod-ing was based on the ISO MPEG draft specificationfor the transportation of moving images over com-munication data networks ADTV modified theMPEG standard to handle the more stringent require-ments of HDTV, and it referred to its scheme asMPEG++ After video and audio signals were digi-tized and encoded, the transport encoder separateddata into two streams in order of their importance

to overall system operation Data critical for taining the basic integrity of received pictures — typi-cally the gray-scale levels, audio signals, data-cellheaders and motion descriptors — were assignedHigh Priority (HP) The low-frequency coefficients andthen the higher frequency (fine detail) coefficientsformed the Standard Priority (SP) data stream As-signment states were adaptive, so SP data could tran-scend to the HP stream when HP loading was light.The two streams were formatted into separate 148-byte data transport cells The cell format was similar

main-to data-communication packets The single-byte vice header identified the type of data being carried

ser-in the maser-in 120-byte block The two data streamswere quadrature amplitude-modulated onto sepa-rate carriers contained within a 6-MHz band The

HP channel was 960 kHz wide; the SP channel cupied 3.84 MHz, and was filtered to have mini-mum power at the NTSC carrier frequencies ADTVreceivers had similar functioning filters so that a co-channel NTSC station did not interfere with HDTVreception

oc-advanced editing Special VCR features to assist in

making glitch-free, professional-looking edits Suchfeatures may include assemble editing, edit preview,digital image superimposer, and the flying erasehead

advanced systems See System terminology.

advanced television A family of TV systems that

im-prove the quality of standard TV This includes EDTV,IDTV, HDTV

Advanced Television Systems Committee The

ne-cessity for standardizing the HDTV format in theUnited States required the FCC to make a choicethat would have a large economic impact To makethe choice with impartiality and expertise, the FCCappointed an ad hoc committee, the ATSC, to studycompeting proposals, including field testing, andmake a recommendation to the FCC

addressable converter

Advisory Committee on Advanced Television

Ser-vice Established in 1987 at the request of the United

States television broadcast industry The original plan

was to develop an advanced television system using

reserved, but unassigned, frequency spectrum

An-other objective became the development of a

digi-tal HDTV standard

AES/EBU digital audio interface A commonly used

digital audio interface specified as a result of

coop-eration between the Audio Engineering Society and

the European Broadcasting Union It is a serial

trans-mission format for two-channel linearly represented

digital audio data Each audio sample is carried by a

sub-frame containing: 20 bits of sample data, 4 bits

of auxiliary data (which may be used to extend the

sample to 24 bits), 4 other bits of data and a 4-bit

preamble Two sub-frames make up a frame that

contains one sample from each of two audio

chan-nels Frames are further grouped into 192 frame

blocks AES/EBU signal includes channel status data

containing information about signal emphasis,

sam-pling frequency, channel mode (stereo, mono, etc.),

use of auxiliary bits (extend to 24 bits or other uses),

and a CRC (cyclic redundancy code) for error

check-ing There are several allowed sampling frequencies

within the 32-kHz to 48-kHz range, the most

common being 44.1 and 48 kHz

AFC Abbreviation for automatic frequency control.

AFM See Beta hi-fi.

AFT Abbreviation for automatic fine tuning.

afterglow See Persistence.

AFV Abbreviation for audio-follows-video.

AGC Abbreviation for automatic gain control.

aggregate Gathered into, or considered as, a whole.

A picture image is perceived as an aggregate of

in-dividual points

agile receiver A satellite receiver that can be tuned to

any desired channel

AIF Audio Interchange File An audio file format

de-veloped by Apple® Computer to store high quality

sampled sound and musical instrument information

aircraft flutter Sudden changes in the quality of a TV

picture, caused by the reflection of the TV signal

from an aircraft flying somewhere over the direct

path between a transmitter and receiver The

re-flected signal interferes with the normal signal at

the receiving antenna

airplane flutter See Aircraft flutter.

airwaves Slang for radio waves, used in radio and TV

broadcasting

ALC Abbreviation for automatic level control or

auto-matic light control

alfecon An iron/silicon/aluminum alloy, used for video

heads

alfesil An iron/silicon/aluminum alloy, used in video

heads

algorithm A formula, or set of steps, used to simplify,

modify, or predict data Complex algorithms are used

to compress files and reduce high digital video andaudio data rates

alias See Aliasing.

alias frequency An erroneous lower frequency

ob-tained when a periodic signal is sampled at a rateequal to or less than twice the signal’s frequency

aliasing Distortion in a video signal It shows up in

different ways depending on the type of aliasing inquestion When the sampling rate interferes withthe frequency of program material the aliasing takesthe form of aliasing frequencies that are known assidebands Spectral aliasing is caused by interferencebetween two frequencies such as the luminance andchrominance signals It appears as herringbone pat-terns, wavy lines where straight lines should be andlack of color fidelity Temporal aliasing is caused wheninformation is lost between line or field scans Itappears when a video camera is focused on a CRTand the lack of scanning synchronization produces

a very annoying flickering on the screen of the ceiving device In sampling, aliasing is the impair-ment produced when the input signal contains fre-quency components equal to or higher than half ofthe sampling rate Typically produces jagged steps

re-on diagre-onal edges See also Nyquist limit Syn.: alias.

aliasing noise A distortion component that is created

when frequencies present in a sampled signal areequal to or greater than one-half the sample rate

alignment In VCRs, the angle the video heads make

with the tracks on the videotape Misalignment ten causes distortion, signal loss, video noise andsnow May also refer to TV tuners and IF amplifiersoperating at the correct frequency

of-alignment disc See Test disc.

alignment tape A special-purpose videotape

contain-ing audio and video reference signals that are used

to correctly adjust the recording and playback heads

of VCRs Alignment tapes are produced by facturers and are not generally available to the pub-lic They are normally for use within the companyand its authorized service centers

manu-alkali metal An manu-alkali-producing metal, such as lithium,

cesium, or sodium, that has photoelectric teristics Commonly used in phototubes and cam-era tubes

charac-all-channel tuning The ability of a TV or VCR to

receive all the available channels

all-digital This term means that everything is done

digitally—storage, processing, editing, etc Noanalog signals are present in the system

alpha See alpha channel and alpha mix.

alpha channel The alpha channel is used to specify

an alpha value for each sample The alpha value isused to control the blending, on a sample-by-samplebasis, of two images: new pixel = (alpha)(pixel Acolor) + (1 - alpha)(pixel B color) Alpha typically has

a normalized value of 0 to 1 In a computer ment, the alpha values can be stored in additional

environ-alpha channel

bit planes of frame buffer memory A 32-bit frame

buffer actually has 24 bits of color, 8 each for red,

green, and blue, along with an 8-bit alpha channel

Also see Alpha mix.

alpha mix This is a way of combining two images

using the alpha channel The box that appears over

the left-hand shoulder of a news anchor is put there

by an alpha mixer Wherever the samples of the little

box appear in the frame buffer, an alpha number of

“1” is put in the alpha channel Wherever they don’t

appear, an alpha number of “0” is placed When

the alpha mixer sees a “1” coming from the alpha

channel, it displays the little box Whenever it sees a

“0,” it displays the news anchor (Of course, it

doesn’t matter if a “1” or a “0” is used, but you get

the point.)

alpha wrap When the videotape almost completely

encircles the head drum of the VCR, permitting the

use of only one head

alphabetic Pertaining to letters of the alphabet.

alphageometric In videotex, simple picture

descrip-tion instrucdescrip-tions that enable line drawings, colored

polygons, curved lines, etc., in addition to text, to

be displayed An accepted standard for

alphageometric display is the North American

Pre-sentation Level Protocol Syntax (NAPLPS) See

Alphamosaic, Alphaphotographic.

alphamosaic In videotex and teletext, a method of

coding that displays a mosaic of 2 x 3 rectangles

This method uses a simple and inexpensive decoder,

but is restricted to text and graphics that do not

require curved or diagonal lines See Alphageometric,

Alphaphotographic.

alphanumeric Using both letters and numbers.

alphanumeric code Pertaining to a character set that

represents numbers or letters of the alphabet

alphanumeric display The display of information

us-ing only letters and numbers When a display is called

an alphanumeric display, it is usually not capable of

displaying sophisticated graphics

alphaphotographic In videotex, a method of coding

that allows photographic quality images to be

dis-played The time needed for transmission and the

complexity of decoding restricts its use See

Alphageometric, Alphamosaic.

alternate channel selectivity The ability of a tuner to

focus on one channel at a time, while rejecting

inter-ference from adjacent channels The tuner’s ability to

suppress this interference is measured in dB; the higher

the number, the better the performance A rating of

about 80 dB is considered excellent This term should

not be confused with capture ratio, referring to two

channels occupying the same frequency

alternating-current transmission A method of

trans-mission used in TV in which the direct-current

com-ponent of the luminance signal is not transmitted

A direct-current restorer must be used in this form

of transmission See direct-current transmission.

aluminized screen A CRT display that has a thin

coat-ing of aluminum on the back of the phosphor layer.Electrons readily penetrate the coating, activatingthe phosphors to produce an image The aluminumreflects outward light that would otherwise go backinside the tube, thereby improving the brilliance andcontrast of the display Also called a metal-backedscreen, metallized screen, and mirror-backed screen

AM, amplitude modulation A method of encoding

data onto a carrier, such that the amplitude of thecarrier is proportional to the data value

amateur TV (ATV) A part of ham radio in which

hob-byists send and receive TV (also called fast-scan TV)pictures

AMA-type screen Actuated-mirror array (AMA)

dis-play system for civilian uses Developed by DaewooElectronics Co Ltd., Seoul The AMA system can beapplied to almost all kinds of TVs, projectors andlaptop portable displays If used on 40" or largerTVs, it can drastically increase the screen brightnessbecause AMA-type screens are 10 times more effi-cient in light production and 2,000 times quicker inresponse time than LCD screens

ambience Reflected light or sound that reaches the

viewer or listener from a variety of directions Light

or sound waves bounce off the ceiling, walls andother boundaries of an area

ambient light The normal illumination The term is

commonly used with projection TV systems andvideo cameras, since how these devices function inambient light is one method of measuring theireffectiveness

ambient noise Refers to normal background noise,

which can be measured with a sound-level meter

ambient-light filter A filter used in front of a display

to reduce the amount of ambient light reflecting offthe display The filter, generally of a dull finish, can

be incorporated into the faceplate of the display or

it can be a separate sheet of plastic

American Museum of the Moving Image A

show-place that emphasizes the hardware of the TV andfilm industry, including costumes, sets and otherparaphernalia Located in Queens, New York, themuseum exhibits a variety of equipment, rangingfrom 19th-century devices to the Sony Walkman.Other highlights include interactive exhibits, videoart displays, video screenings and a host of consumerproducts based on popular TV shows and personali-ties

American Television Alliance (ATVA) Consists of

General Instrument Corp (GI) and MassachusettsInstitute of Technology (MIT)

AML Abbreviation for amplitude-modulated link AML frequencies In an AML system, there are four

groups of frequencies: C, D, E, and F Group C nels add 12,646.5 MHz to the VHF frequency Group

chan-D channels add 12,705.7 MHz to the VHF frequency.Group E channels add 12,898.5 MHz to the VHF

alpha mix

frequency Group F channels add 12,958.5 MHz to

the VHF frequency

A-mode See MUSE-9 system.

AMOL/SID Abbreviation for Automated Measurement

Of Lineups/Source IDentification An identification

signal included in the vertical blanking interval (VBI),

broadcast by virtually all TV networks It is used by

TV-ratings services to identify the network, show,

date, time, hour, minute and second of a broadcast

As part of the AMOL system, the signal helps a

TV-ratings service verify when specific shows and

com-mercials were broadcast on local stations

amp Short for amplifier.

amplified coupler A device typically used to boost a

TV signal so it can be adequately received by several

TVs and VCRs throughout the home

amplifier A device that outputs a magnified version

of the input signal

amplifier power The amount of magnification an

amplifier can produce, usually specified in watts The

larger the number, the greater the magnification the

amplifier can produce

amplitude Strictly, the peak value of a signal in the

positive or negative direction The difference

be-tween minimum and maximum values is the

peak-to-peak amplitude May also refer to the value of

a signal in the positive or negative direction at a

particular moment

amplitude distortion See Distortion.

amplitude fading See Fading.

amplitude modulation A method of encoding data

onto a carrier, such that the amplitude of the carrier

is proportional to the data

amplitude-modulated link This system converts cable

TV frequencies to microwave frequencies and

trans-mits the signal to a receiving site, where the

micro-wave frequencies are converted back down to the

standard cable TV frequencies The AML system used

by cable operators is called community-antenna

ra-dio service (CARS) and is in the frequency band of

12-12.95 GHz The studio transmitter link AML

ser-vice is used for connecting studio facilities, usually

in a city, to the transmitter or up-link site out of the

city The antenna systems used at these frequencies

are usually parabolic dishes of 4-10 feet in

diam-eter Also see Cable television relay service.

amplitude-shift keying A method of encoding data

onto a carrier, such that a finite number of different

amplitude levels of the carrier are produced

anaglyph An image made up of two slightly different

views, in contrasting colors, of the same subject

When viewed through a pair of corresponding color

filters, the image seems three-dimensional

anaglyphic method A three-dimensional viewing

method based on colored light, such as the familiar

red and green viewing glasses It usually yields

im-perfect pictures because the filters fail to eliminate

the complementary color completely

analog The representation and measurement of the

performance or behavior of a system by ously variable physical entities such as current, volt-ages, etc Analog data yields an exact replication ofthe original information Most conventional VCRs,for example, record information using the analogprocess Analog differs from digital, which duplicatesinformation in a discrete, or discontinuous, form, aswith more advanced VCRs

continu-analog active lines See Active lines.

analog active part See Active part.

analog channel A transmission channel that is used

to transmit an analog signal

analog component format A format that uses three

signals to specify color and brightness The mostcommon video formats are YPbPr and YUV

analog component video See Analog component

format.

analog encryption A video scrambling method that

operates within the standard video bandwidth Someapproaches may result in degradation of the origi-nal video signal when it is decoded

analog monitor In reality, all displays based on CRT

technology are analog Some analog monitors areincorrectly called digital monitors since they ac-cept digital signals, and convert them to analoginternally

analog signal processing The conventional method

used by audio and video equipment manufacturers

to reproduce a signal A broadcast signal is produced

in the shape of a series of waves, each wave heightrepresenting voltage while the distance betweenpeaks in these waves determines the frequency ofthat part of the signal These components of thesignal, along with others, are separated, amplifiedand fed into VCRs, TV sets and so on for reproduc-tion Much of the original quality of the signal, how-ever, is lost through this process, although some unitsare better able to rebuild the signal than others,thereby producing a better picture A more sophis-ticated approach to reproducing a signal is by means

of digital signal processing

analog tuning A method of tuning a TV, VCR, etc.

Analog tuning permits setting the system to anychannel within its frequency range This tuner, be-cause of its manual capability, either of the mechani-cal or electronic variety, differs from the frequency-synthesis tuner, that is preset

analog video Video signals that use a

continuous-time signal, with varying amplitude

analog/digital converter See Analog-to-digital

converter.

analog-to-digital converter A device that transforms

a signal from analog form to digital form This isdone by taking samples of the analog signal at regu-lar intervals Each analog sample value is then con-verted into a binary code For video applications,additional functions are usually incorporated, such

analog-to-digital converter

as automatic gain, filtering and black level

clamp-ing An ADC for digitizing video must be capable of

sampling at 10 to 150 million samples per second

Sometimes also called a digitizer

analogue The European spelling of analog.

anamorphic Viewed picture format with geometric

deformation of the wide-screen picture aimed to

achieve full vertical screen occupation while using

the conventional TV display

anamorphic lens A special camera lens that allows

the user to make videotapes in wide-screen format

using a standard video camera

ANC/WNL Abbreviation for Automatic Noise

Cancel-ing and White Noise LimitCancel-ing These circuits are in

some TVs to process the video and sound signals

ancillary data Non-video data transmitted within a

digital video data stream, usually during the

hori-zontal and vertical blanking intervals It may be digital

audio, teletext, etc

ancillary timecode BT.1366 defines how to transfer

VITC and LTC as ancillary data in digital component

interfaces

angle modulation Modulation where the angle of a

sine-wave carrier is the characteristic varied from its

normal value Phase modulation and FM are

par-ticular forms of angle modulation

angle of view (AOV) The area or width of a subject or

scene that a lens takes in or covers The AOV

de-pends on the focal length of the lens and is given by

the equation cot A/2 = 2F/W, where A is the AOV, F

is the focal length of the length and W is the width

of the photosensitive surface The smaller F, the

greater the AOV For example, a 12.5mm focal length

has a wider angle than a 75mm lens

ANIK The name given to Canadian TV, and more

re-cently, to Canadian TV satellites ANIK is an Inuit

word meaning “brother.” ANIK satellites have both

4-GHz C-band and 12-GHz Ku-band transponders

animation Also called time lapse See Frame-by-frame

recording, intervalometer, interval timer, optical

ani-mation, pipeline architecture, pixilation, time lapse

video.

anode-voltage-stabilized camera tube Syn.:

high-electron-velocity camera tube See Camera tube See

also Iconoscope.

anomalistic period The interval of time between one

passage of a satellite through its apogee and the

next consecutive passage

anomalous propagation Accidental transmission of

VHF radio waves beyond the horizon, probably

caused by temperature inversion in the lower

atmo-sphere

ANSI Abbreviation for American National Standards

Institute This organization sets standards for the

computer languages, electrical specifications,

com-munications protocols, etc

antenna In TV, that part of a transmitter or receiver

facility that sends out waves into or accepts them

from the air Also, a wire or set of metal rods structed for the purpose of intercepting waves inthe air and changing them into an electrical signalthat is sent to a TV receiver TV antennas are af-fected by various external factors, such as the loca-tion of the transmitters, the contours of the landand certain obstructions, and the physical condition

con-of the antenna and connecting cables Most nas (except satellite dishes) utilize the dipole tech-nique: two equal rods or arms, each as long as 1/4the wavelength of the anticipated signal The an-tenna lead-in is located at the center of the two arms.Since direction is important for maximum reception,most antennas have a combination of reflecting rodsand directors (shorter rods) to provide additional di-rectivity Commercial TV antennas are usually de-signed for local (15-20 miles), suburban or mid-range(20-30 miles), or fringe use

anten-antenna combiner A device that combines the

sig-nals from several antennas, each of which is aimed

at a different TV station Antenna combiners arehelpful where all the TV transmitters are not located

in a single direction

antenna coupler A device that is used when more

than one TV is connected to a single antenna Alsoknown as an antenna splitter, it helps prevent im-pedance mismatch and interference between TVs.Several commercial types are available The resistanceantenna splitter prevents some impedance mismatchand offers some isolation, but contributes to a re-duction in signal strength The transformer antennasplitter reduces both impedance mismatch andinsertion loss

antenna farm The location for the transmitting

an-tennas for most or all of the TV stations in an area

antenna rotator A small motor mounted externally on

an antenna mask and remotely controlled to adjustthe antenna direction so that it receives the best pos-sible signal from a TV station In some areas wheremultiple TV stations do not transmit their signals from

a central location, a single dipole antenna is not fective Either several antennas or a single antennawith a rotator must be used for best reception

ef-antenna splitter See Antenna coupler.

antenna-switching circuitry Controls to select

alter-nate inputs to the TV set (pay decoder, TV games,VCR, etc.) Found in the front-end stages of some

TV sets It improves reception of cable-TV signals

anti-alias filter A filter (typically a lowpass filter) used

to bandwidth-limit a signal to less than one-half thesampling rate Also called an anti-aliasing filter

anti-aliasing The process of smoothing jagged edges,

especially along curved or diagonal edges of played objects, such as graphics and text

dis-anti-aliasing circuitry An electronic circuit that

per-forms anti-aliasing Many professional charactergenerators offer anti-aliasing as one of their features

anti-aliasing filter See Anti-alias filter.

analogue

anti-comet tail gun A device in a TV camera tube to

reduce or eliminate streaks, called comets

anti-copy signal See Anti-piracy signal.

anti-logarithmic amplifier Used in 3D-image TV

cam-era systems to form a depth video signal

Antiope The French teletext system.

antiPAL test pattern A video signal that has a

delib-erately wrong PAL switch function The polarity of

the U component, instead of the V component, is

switched This enables measuring the performance

of the line averaging function in the PAL decoder

When it works correctly, the display has no color

since the antiPAL chrominance is cancelled by the

decoder’s line averaging

anti-piracy signal A method of preventing

pre-re-corded videotapes from being “pirated” or

dupli-cated illegally One system places a special signal

electronically on the tape; another modifies the

hori-zontal and vertical sync pulse and the color burst

phase, causing rolling or other forms of instability in

the picture during the copying process Supposedly,

this signal has no effect during playback on a TV

set Also called anti-copying signal

anti-reflection coating A thin coating deposited on

the surface of glass to reduce reflection of ambient

light

anti-top flutter pulse Disables the phase detector

during equalization and framing times

AO A category of the movie rating system that

indi-cates the program is for adults, 18 and older

AOD Abbreviation for audio optical deflector.

AOM Abbreviation for audio optical modulator.

APC Abbreviation for automatic phase control.

APEL Abbreviation for Advanced Product Evaluation

Laboratory

aperture An opening through which electrons, light,

radio waves, or other radiation can pass The

aper-ture in the electron gun of a CRT determines the

size of the electron beam The aperture in a TV

cam-era is the effective diameter of the lens that controls

the amount of light entering the camera tube The

dimensions of the horn mouth or parabolic

reflec-tor determine the aperture of a microwave antenna

The aperture in a lens is an adjustable orifice

con-trolling the amount of light transmitted by a lens

The maximum diameter of the aperture in relation

to the focal length of the lens determines its

theo-retical speed Its effective speed depends also on

the transmission of the glass elements of the lens

aperture correction Method of compensating for loss

of higher picture frequencies caused by the

scan-ning spot in a camera tube having a finite size, and

thus failing to respond sharply to sudden vertical

boundaries between dark and light areas Consider

a square spot of finite size scanning a sharp

black-to-white transition The resulting signal output

changes level with a linear slope In practical

elec-tron devices the spot tends to be circular or nearly

so, and to have a Gaussian distribution of energy,

so that the signal changes with a more rounded sition This effectively reduces the high frequencycontent of the signal, and compensation must bemade by increasing the gain in the high frequen-cies, taking care not to exceed the bandwidth ofthe channel or unduly increase noise or introducephase distortion

tran-aperture corrector An equalizer designed specifically

to offset aperture distortion

aperture delay The time from an edge of the input

clock of the ADC until the time the ADC actually takes

the sample The smaller this number, the better

aperture distortion Attenuation of the high-frequency

components of a TV picture signal caused by thefinite cross-sectional area of the scanning beam inthe camera The beam then covers several mosaicglobules in the camera simultaneously, causing loss

of picture detail

aperture grille A slotted metal screen located just

behind the inside of a TV display tube’s screen face, used to limit the points at which the electronshit the phosphor coating of the screen A Sony in-vention, the function is similar to that of a shadowmask, the purpose of both being to ensure the re-

sur-production of a true color TV picture See also Color

picture tube.

aperture jitter The uncertainty in the aperture delay.

The aperture delay time changes a little bit each time,and that little bit of change is the aperture jitter

aperture mask Shadow mask An opaque disk

be-hind the faceplate of a color picture tube; it has aprecise pattern of holes through which the electronbeams are directed to the color dots on the screen

aperture reduction ring An accessory on some

pro-jection TV systems to make the image appear sharper

by cutting down on the f stop, or aperture, of the

projecting lens The disadvantage is that using asmaller aperture also decreases the amount of lighttransmitted to the screen

aperture response The aperture response of a

com-ponent or system is a graph of the peak-to-peakamplitude of its response (e.g., of the variations inreflected light) as a function of the TV line number.Assume that a pattern of black-and-white lines ofvarying widths is scanned by a narrow light beam,and the peak-to-peak variation in the reflected lightfrom the black and light lines is measured On linesthat are much wider than the diameter of the spot,these variations will be of full amplitude As the width

of the lines is decreased so that the scanning spotalways overlaps a portion of black and white line,the amplitude of the variations will decrease Whenthe width of the lines is twice the diameter of thespot, the variations disappear The width of theselines is specified by its reciprocal, the number of al-ternate black and white lines (counting both blackand white lines) that can be fitted into the vertical

aperture response

dimension of the picture This parameter is known

as the TV Line Number The aperture response of a

component or system can be specified either by its

response to a square-wave pattern, i.e., alternate

dark and light bars, known as the contrast transfer

function (CTF), or by its response to a theoretical

pattern in which the cross-sectional darkness of the

bars varies sinusoidally, the modulation transfer

func-tion (MTF) The CTF is physically measurable, but

the MTF is more useful for analytic purposes

Aper-ture response is a universal criterion for specifying

picture definition and other aspects of imaging

sys-tem performance It can be used for film images,

camera lenses, TV camera imagers, video amps and

other bandwidth-limiting components, the scanning

process, receiver picture tubes, and the human eye

aperture slit In 3D-image display with parallax

bar-rier, an interval between the stripe barriers A viewer

observes the displayed image through the aperture

slits by both eyes

APL Abbreviation for average picture level.

apochromatic lens A lens that has been corrected for

chromatic aberration for three colors

apple tube A color CRT with vertical red, green, and

blue phosphor stripes The spacing varies at the top

and bottom of the CRT, so the face somewhat

resembles an apple

Applegate diagram A diagram used to illustrate the

principle of electron bunching in velocity-modulated

tubes (e.g., klystron, traveling-wave tube)

APT Abbreviation for automatic picture transmission.

APTV Abbreviation for Associated Press TV.

Aquadag A trademark of Acheson Colloids Co for

their brand of colloidal graphite in water, widely used

to produce a conductive coating on the inside

sur-face of the glass envelope for CRTs, where it

col-lects secondary electrons emitted by the fluorescent

screen Also used on the outside of some picture

tubes, where it serves as the final capacitor of the

high-voltage filter circuit

ARC Abbreviation for adaptive range coding.

arc of good location The portion of the

geosynchro-nous orbit (22,300 miles above the equator) that

provides optimum coverage of a country

archiving The storage of TV shows, movies and other

programs for future playback

arcing A curved movement, as in the circular motion

of a TV pedestal camera, for which the instructions

are “arc left” and “arc right.”

ARO Abbreviation for Audio Receive Only, small dish

antennas used by radio networks for music and news

programming distribution from TV satellites

A-roll The primary material, as opposed to B-roll In

video editing, alternate scenes are arranged on two

reels (A-roll and B-roll) and then assembled

ARS board RF record/playback amplifier, servo circuit,

and audio signal record/playback circuit; Betamax

VCR

art card A cardboard (generally 11"x14") with a dark

background and light letters (although it may beblack letters on a white background) As used in TV,

it contains credits and other information and ismounted on an easel in front of a TV camera

Article 810 See National Electrical Code.

artifacts Distortions in a video signal; spurious signals

created artificially (hence the term artifact) by theimaging process One of the most common is cross-luminance, a characteristic of composite systemsemploying a color subcarrier It is a dot pattern thatresults from failure of the subcarrier signals on suc-cessive frames to cancel each other completely, e.g.,

on vertical edges of areas with high saturation Theycan also be produced by moving objects in an inter-laced scanning and appear as interline flicker Theycan be eliminated or greatly reduced by the use ofprogressive scanning and component color systems

In the video domain, artifacts are blemishes, noise,snow, spots, etc When you have an image artifact,something is wrong with the picture from a visualstandpoint Don’t confuse this term with not hav-ing the display properly adjusted For example, if thehue control is set wrong, the picture will look bad,but this is not an artifact An artifact is some physi-cal disruption of the image

artificial HDTV See Osborne compression system artificial satellite See Satellite.

Arts & Entertainment A cable TV advertiser-supported

network specializing in cultural programs, taries, variety shows and chiefly foreign feature films

documen-ASC 1 American Society of Cinematographers 2.

Active Signal Correction Syn.: fuzzy logic (in Sonyusage—see, e.g., KV-27XBR50, Sony monitor/receiver)

ASCII American Standard Code for Information

Inter-change, a code for transmitting data, made up of

128 letters, numbers, symbols, and special codeseach represented by a unique binary number

ASIC Application specific integrated circuit.

ASK Abbreviation for amplitude-shift keying aspect ratio The width-to-height ratio of a display It

is usually expressed as two numbers separated by acolon (width:height), such as 4:3 or 16:9 It may beexpressed as a normalized single number, such as1.33 A 35-mm frame of film measures 36 x 24 mm,meaning it that it has an aspect ratio of 3:2 Since it

is different in size from a 4:3 or 16:9 TV screen, alittle bit of the sides or tops of movies are choppedoff when displayed on TV

aspect ratio conversion Conversion of the TV

pic-ture geometry preserving the scanning standard,e.g., from the so-called anamorphic format toletterbox format The video signal itself is aspect-ratio independent

aspheric corrector plate Lens, one surface of which

is specially shaped and is not part of the surface of asphere as are the surfaces of most lenses Used in

aperture slit

some large-screen TV projectors and some

wide-range room lenses

ASR Abbreviation for automatic standard recognition.

assemble edits Edits that record all aspects of the

program (audio, video, and control) at the same time

assembly edit VCR feature that allows for clean

tran-sitions when adding audio or video sequences to

prerecorded material Also an editing technique in

which pretaped segments are rerecorded end-to-end

in a preferred order with selected transitions

astigmatism 1 A type of spherical aberration in which

light rays from a single point of an object do not

converge at the corresponding point in the image

2 A defect in an optical or electron lens that causes

focusing in different axial planes to occur at

differ-ent points along the lens axis As a result of

astig-matism, a point object gives rise to an image in the

form of a horizontal line at another point Normally

the best compromise is between these two points

where the image has the form of a circle of least

confusion, representing equal vertical and

horizon-tal resolution

Astra Luxembourg’s broadcast satellite Frequency

band: 11.2-11.45 GHz Channels: 16 transponders

Polarization: linear

Asymmetric Digital Subscriber Line See ADSL.

asymmetrical compression Techniques where the

decompression process is not the reverse of the

com-pression process Asymmetrical comcom-pression is more

compute-intensive on the compression side so that

the decompression of video images can be easily

per-formed at the desktop or in applications where

so-phisticated codecs are not cost effective In short, any

compression technique that requires a lot of

process-ing on the compression end, but little processprocess-ing to

decompress the image Used in DVD-Video creation,

where time and cost can be incurred on the

produc-tion end, but playback must be inexpensive and easy

asymmetrical-sideband transmission Vestigial

side-band transmission

asynchronous Refers to circuitry and operations

with-out common timing (clock) signals

asynchronous transfer mode (ATM) The technology

selected by the CCITT in 1988 to realize a B-ISDN It

is a fast, cell-switched technology based on a

fixed-length 53-byte cell All broadband transmissions

(whether audio, data, imaging or video) are divided

into a series of cells and routed across an ATM

net-work consisting of links connected by ATM switches

Each ATM link comprises a constant stream of ATM

cell slots into transmissions that are placed or left

idle, if unused The most significant benefit of ATM

is its uniform handling of services allowing one

net-work to meet the needs of many broadband

ser-vices ATM accomplishes this because its

cell-switch-ing technology combines the best advantages of

both circuit-switching (for constant bit rate services

such as voice and image) and packet-switching (for

variable bit rate services such as data and full tion video) technologies The result is the bandwidthguarantee of circuit switching combined with thehigh efficiency of packet switching

mo-asynchronous transmission The transmission mode

by which characters may be sent with random ing The data bits of each character are introduced

tim-by a start bit and followed tim-by a stop bit The chronous mode is common for low-speed transmis-sion, less than 2.4 Kbps

asyn-ATC See ancillary timecode.

ATM See Asynchronous Transfer Mode.

atomic bomb wipe A transition in which a scene is

slowly moved up on the screen (suggesting an atombomb cloud) as it is replaced by another scene

ATR Abbreviation for audio tape recorder.

ATSC Advanced Television Systems Committee, a

pri-vate sector organization founded in 1982 to developvoluntary standards for the entire spectrum ofadvanced television systems, including high defini-

tion (HDTV) See HDTV.

ATSC A/49 Defines the ghost cancellation reference

signal for NTSC

ATSC A/52 Defines the (Dolby Digital) audio

compres-sion for ATSC HDTV

ATSC A/53, A/54 Defines ATSC HDTV for the USA ATSC A/57 Defines the program, episode, and version

ID for ATSC HDTV

ATSC A/58 PSIP for Taiwan.

ATSC A/63 Defines the method for handling 25 and

50 Hz video for ATSC HDTV

ATSC A/65 Defines the program and system

informa-tion protocol (PSIP) for ATSC HDTV

ATSC A/70 Defines the method for conditional access

for ATSC HDTV

ATSC A/90, A/91 Defines the data broadcast

stan-dard for ATSC HDTV

ATSC A/92 Defines IP multicasting using data

broad-casting for ATSC HDTV

attached A physical channel of a digital picture

ma-nipulator is said to be attached to a logical channel

of a controller when the physical channel is fully acquired by the controller

success-attenuation cable A cable designed to connect the

line-level audio output of one device to the level microphone input of another device

low-attenuation distortion Syn frequency distortion See

Distortion.

attributes display In videotex, a means of modifying

the presentation of characters on the screen tributes may be applied to the full screen, a full row,part of a row (serial), or to subsequently printedcharacters (parallel)

At-ATV Abbreviation for Advanced Television or amateur

television 1 Advanced Television Refers to any type

of advanced TV system not presently in general use

or production The most recent example of ATV isthe HDTV system now reaching the marketplace

ATV

ATV standards in North America include standard,

enhanced, and high-definition versions Although

ATV systems are collectively considered to offer

bet-ter quality than the NTSC signal, they can carry

multiple pictures of lower quality and can also

sup-port the cancellation of artifacts in ordinary NTSC

signals 2 Amateur TV Sending pictures by

ama-teur radio You’d expect this abbreviation to apply

equally to fast-scan TV (FSTV), slow-scan TV (SSTV)

and fax, but it’s generally applied only to FSTV

ATV identification Short for Amateur TV identification.

ATVA Abbreviation for American Television Alliance.

ATVA-P 6-MHz simulcast HDTV/EDTV format Scanning:

787.5/59.94, sequential; channel coding: digital The

signal is sampled initially at a rate well above the

Nyquist limit By various bandwidth reduction

tech-niques, the bit rate is brought within the capacity of

a 6-MHz frequency band

AU (also SND) Interchangeable file formats used in

Sun and other workstations Basically it is a raw

audio data format preceded by a header

audimeter An early device attached to home TV sets

and designed to measure a family’s viewing habits

Placed in representative homes, it was used by the

A.C Nielsen Company to measure the popularity of

TV shows The rating information determined the

advertising rates of the shows and which shows

would be renewed or cancelled In addition, the

rat-ings revealed which channel or channels were

watched the most

audio Latin for “I hear.” Used to describe frequencies

capable of being heard by the human ear, between

15 Hz and 20 kHz The sound segment of a

video-tape, VCR, VDP or other component Also, the input,

output, cable wire, attachment or other feature,

ac-cessory or software referring to the sound portion of

a system For example, there are audio inputs, audio

cables, audio mixers, etc Slang for sound

audio alarm A feature that presents an audible signal

to tell the user that certain functions have been

ac-tivated For instance, some VCRs beep once when

recording begins and twice when it ends

audio bandwidth In reference to videotape, the

pa-rameters or audio range of a tape Although

hu-man hearing can respond to frequencies from

ap-proximately 15 or 20 Hz to 20 kHz, the audio

por-tion of a videotape has a bandwidth that is much

shorter, somewhere from 50 Hz to 10 kHz,

depend-ing on certain tolerance limits measured in dB This

poorer response is caused by the small area of the

tape allotted to the audio track and by the extremely

slow speed at which the tape travels past the audio

head Higher-quality tapes extend these numbers on

both ends of the bandwidth to produce less

distor-tion, hiss, etc However, the audio bandwidths of

most tapes do not present any true limitations to

many low-priced VCRs since these machines have

an even shorter range than that of the videotape

audio cable tester A device designed to check cables

for shorts, phasing, continuity, etc Used mostly byprofessionals, the cable tester is used with standardXLR3 pin-type cables and 3-conductor phone plugs

audio cue The identification of an event by the use of

a sound to alert those producing either an audio orvideo tape to the fact that something is about tohappen In video productions, certain words in thescript are used as “cues” to denote shifts in action,camera position, microphones, or other technicalevents; in electronic editing, audio cues are oftenused to signal edit points

audio decoder Accessory used in conjunction with

VCR-equipped stereo sound to send the signals tovarious speakers for the purpose of creating a the-atrical effect at home The audio decoder picks upthe encoded stereo track on the videotape and in-terprets the appropriate paths for the signal,directing it to front, back and side speakers

audio demodulation circuit A circuit to separate the

audio information from its carrier This carrier is tually a subcarrier that is impressed onto the videocarrier

ac-audio distribution amplifier A device designed to

improve the sound quality of videotapes A typicalmodel contains a special filter circuit that decreasesbuzz and other noise, a microphone input for mix-ing sound-on-sound or adding narration, bass andtreble tone control, etc Some models provide a by-pass feature for comparison of the affected andunaffected signal The amp is often used to preventgeneration loss of audio when duplicating tapes

audio dub To rerecord the audio portion of a video

tape without disturbing the video portion of the nal; also, to make a copy of an audio tape

sig-audio dubbing narration The addition of narration

to a videotape The process requires the followingsteps: Connect an external microphone into the micinput of the VCR If you decide to use the built-inmic of the video camera, connect the camera to theVCR Turn down the volume of the TV set to avoidfeedback Press Audio Dub, start the tape and thenarration

audio dubbing recorded music The addition of

mu-sic to a previously recorded videotape One simpleprocedure is to place the mic next to one of thespeakers and switch the sound system to mono.Another, more desirable, method is to connect theamplifier or receiver of a stereo system or an audio-tape recorder to the audio input of the VCR

audio equalizer See Equalizer.

audio essay A discussion of a specific film or program

added to a commercial videodisc or videotape ally applied to classic works, the audio essay, whichutilizes one of the stereo channels, presents an “ex-pert” who takes the viewer on an oral and visualjourney of the production The historian or criticcovers such items as biographical information per-

Usu-ATV identification

taining to the performers or director, missing or

added scenes, interviews and related still shots and

trailers

audio expander A feature on an audio processor to

improve the dynamic range of sound

audio expansion circuitry A development found in

TVs to provide a simulated stereo effect when

re-ceiving monaural broadcasts, cable TV, or signals

from monaural external units (VCR, video disc player,

etc.) connected to the rear panel audio/video inputs

audio for video The term to describe two

compo-nents of audio production used in the video

me-dium: 1 High-quality stereophonic audio 2

Multi-track production techniques The adaptation of these

components for the medium of video has given

pro-duction teams the ability to further improve TV

through the introduction of creative, high-quality

audio

audio frequency modulation (AFM) See Beta hi-fi.

audio head In video, a stationary magnetic head

ca-pable of recording and playing back sound signals

After receiving the audio signal, the head pulses it

onto the videotape during recording or takes it from

the tape for reproduction during playback The

au-dio head is the third and last process that affects

the videotape The erase head is the first, followed

by the video heads The audio head assembly is

sometimes called the audio/control head and

con-tains three heads One performs the audio

record-ing and playback, the second is designed for audio

dubbing and the third is the control track head that

transmits pulses onto the tape to control the start

of each alternate field, that is, to track the original

recorded signal

audio input A jack, often located at the rear of a VCR

and TV, that accepts audio signals

audio modulation Refers to modifying a carrier with

audio information so that it may be mixed with the

video information and transmitted

audio optical deflector (AOD) In 3D viewing systems,

a device that serves as a horizontal scanning

sys-tem

audio optical modulator (AOM) In 3D viewing

sys-tems, a device that serves as an optical modulating

system The incident laser beam is intensity

modu-lated by the AOMs in response to a video signal

audio output A jack, often located at the rear of a

VCR, DVD player, and TV, that outputs audio

sig-nals One, two (for stereo), or six audio outputs may

be present

audio plug The metal connector at either end of an

audio cable that fits into component receptacles

called jacks The three basic types of audio plugs

used in home video are mini-plugs, phono plugs and

phone plugs The mini-plug is a smaller version of

and similar to the phone (for telephone) plug Both

have a shaft that protrudes from a metal sleeve The

phono (from phonograph) plug, often referred to

as an RCA-type plug, also has a small shaft, but it issurrounded by a petal-shaped metal cup

audio processor A device that can be used in audio;

e.g., between a VCR and a stereo system The audioprocessor usually contains such features as inputsfor microphones, VCRs and tape; a multiple-bandequalizer for improved sound; a stereo delay simu-lator and an audio expander to extend thedynamic range of the sound signals

audio response The ability to reproduce audio

sig-nals Better-quality videotapes, especially those listed

as HG (high grade), produce less hiss, or an average signal-to-noise ratio Tapes of poorer qual-ity cause more audio distortion, hiss, etc Audio re-sponse becomes more critical in the slower speedmodes of both Beta and VHS machines The aver-age listener can respond to frequencies from ap-proximately 20 Hz to 20 kHz Videotape, however,falls short of this range, and is somewhere between

above-50 Hz and 10 kHz Distortion and poor responseresult beyond these parameters Tapes that exceedthis audio bandwidth range (within certain tolerancelimitations measured in dB) may be considered bet-ter than average, although most home video ma-chines have a range narrower than that of mosttapes DVD-Video and DVD-Audio offer much im-proved audio capabilities over videotapes

audio signal An electrical signal whose frequency falls

within the audible range, the lowest measured atabout 15 to 20 Hz and the highest at approximately

20 kHz

audio signal-to-noise ratio In videotape, a

measure-ment that determines the loudness of an undistortedsignal relative to tape noise Audio signal-to-noiseratio is measured in dB The larger the number, thebetter the audio quality of the tape

audio subcarrier The carrier wave that transmits

au-dio information within a video broadcast signal.Audio subcarriers are frequency modulated They aretransmitted above the video, in the 4.5 to 8.0 MHzrange for NTSC and from 5.5 to 8.5 MHz for PAL/SECAM broadcasts

audio/control head See Audio head.

audio/video amplifier An accessory that adds sound

processing to videotapes The unit usually comesequipped with multiple audio/video inputs and out-puts on its rear panel and digitally delayed audiomodes that offer such special effects as stage, sta-dium, theater and matrix The switchable amplifiermay power several channels, depending upon thewatts-per-channel used Some models accommodateS-VHS and ED-Beta formats and feature a title gen-erator and a video enhancer

audio/video combiner Device serving to embed

sev-eral digital audio signals within a digital video signalstream (usually using a serial digital interface)

audio/video dub A video camera feature that

per-mits the replacement of a current segment of audio

audio/video dub

and video information on tape with new material.

When audio/video dub is activated, new

informa-tion is inserted over both tracks Most present

cam-eras offer this feature while other models provide

only audio dub

audio/video input Basic RCA jacks found on VCRs

and TV monitor/receivers Stereo models provide one

input for video and two for audio Mono units offer

only one audio and one video jack

audio/video memory function A feature, found on

some TVs, that permits optimum control set-ups to

be stored in memory for later recall

audio/video mixer An editing accessory that allows

switching back and forth between two video sources,

such as two VCRs or a VCR and camcorder Some

A/V mixers offer additional features such as a fader,

wipe effects and special-effects generator There are

manual and electronic mixers The electronic type

may use computer software and IR technology to

“learn” the tape transport commands of the

record-ing VCR The user simply marks and names the

scenes on the footage to be edited and instructs

the mixer that scenes should appear in the final tape

audio/video mute Special electronic circuits designed

to silence a TV set to circumvent annoying noise and

static The mute feature also darkens the screen

when the tuner is between channels or a videotape

ends Muting is sometimes referred to as blanking

audio/video processor A multi-function device for

use with various video components The processor

usually provides inputs and outputs for audio and

video switching, an audio and video distribution

amp, a video stabilizer, an image enhancer, an RF

converter, etc Some sophisticated models may

of-fer color tint control, color intensity control, split

screen enhancer, audio/video mute, a bypass switch

and a fade duration control

audio/video receiver A separate unit designed to

function as a control center of home entertainment

systems These systems usually accommodate

sev-eral audio inputs (CD, phono, tape and line) and

several video inputs (VCRs, DVD and cable/satellite

set-top box) Some units permit two-way dubbing,

includes S-video and component video terminals and

offer memory that can store several surround sound

settings as well as “memorize” 30 stations for

in-stant recall

audio/video signal See Signal.

Audio/Video Support System (AVSS) In DVI runtime

software, the software package that plays motion

video and audio

audio/video switcher See Switcher.

audio-follows-video An advanced feature of a

pro-fessional/industrial editing console or switcher that

permits the audio signal to follow the video edit

operations, thereby facilitating audio crossfades to

be produced under editor control AFV offers a wide

range of possibilities for professional editors Scene

transitions produced in the video mode can matically activate fades between complex audiobalances Thus, video edits and scene transitions cancontain more tightly synchronized crossfades Also,AFV facilitates the addition of music, dialog and spe-cial audio effects to multi-track master tape before

auto-a work print is produced

audio-follows-video switcher A switcher that

changes both audio and video sources with the push

of one button

audio-mix control A stereo VCR feature that

desig-nates the amount of audio each channel feeds tothe mono RF output Table-model and portable ste-reo VCRs produce dual channel sound by means oftwo individual audio tracks laid down on the topportion of the videotape During the normal stereoplayback, both tracks are utilized The audio-mixcontrol, however, permits an increase in either left-

or right-channel sound by simply rotating the knob

audition The preliminary studio test of a performer,

act, or complete program for a TV or radio show

augmentation channel See Terrestrial HDTV

broad-casting, MUSE-9 system.

augmented reality A subset of virtual reality which

attempts to generate a composite view for the user

of the real world combined with a ated virtual scene The technology has applications

computer-gener-in mediccomputer-gener-ine, the military, entertacomputer-gener-inment, and facturing

manu-aural signal The audio portion of a TV signal; the

picture portion is called the video signal

aural transmitter The equipment used to transmit

the audio portion of a TV program The audio andvideo transmitters together make up the TV trans-mitter

AUSSAT Australia’s broadcast satellite Frequency band:

12.25-12.75 GHz, 15 channels Polarization: polarized continental beams

cross-authoring The process of using multimedia

applica-tions to create multimedia materials for others toview Multimedia authoring uses many tools, fromthe text editor or desktop publishing application, totools for capturing and manipulating video images

or editing audio files

authoring platform A computer that has been

out-fitted with the hardware for creating material to beviewed in a multimedia box The video quality ofthe authoring platform has to be high enough thatthe playback equipment is the limiting factor

auto channel search See Automatic channel scan.

auto cue and play Functions of VCRs Just insert a

recorded video cassette without an erasure vention tab and the VCR turns itself on, then skipsover the no-signal portion and immediately startsplayback at the beginning of the recording

pre-auto image stabilization Syn.: Lens stabilization auto lock switch A feature, found on some

camcorders, designed to simplify and speed up the

audio/video input

operation of the camera When the user activates

the Auto lock switch, it simultaneously sets the

auto-focus system, white balance, shutter speed and

back-light compensator

auto play See auto cue and play.

auto program See Automatic channel scan.

auto repeat A VCR feature that allows the viewer to

automatically play back a videotape Auto repeat

differs from repeat play, a feature that plays a

vid-eotape up to a specific point, stops and rewinds to

a previous point, and continues to play that portion

of the tape indefinitely until the button is pressed

again

auto selection tool An imaging term A tool that

se-lects an entire area within a specified range of color

values around a selected pixel

auto start See auto cue and play.

auto tracking A VCR feature that seeks out the most

accurate playback tracking position for a given

vid-eotape Since VCRs differ in their video head

place-ment, some tapes, especially those recorded at the

slowest speed, may not play properly on other VCRs

Many machines come equipped with a manual

ing control to adjust for these variations; auto

track-ing handles these differences automatically

auto/manual aperture control A device that places

the control of the f-stops or aperture openings into

the hands of the user Many camcorders feature

automatic iris control, a less desirable feature for

some camera owners who prefer to make their own

selections Some users choose to open or close the

lens one or two additional stops for special

effects

auto/manual iris control Syn.: Auto/manual

aper-ture control

auto-assemble Generation of an edited master by a

video or audio-for-video edit controller using an

ex-isting edit decision list

autodialer A device which, when activated by a short

code or mnemonic key or, in videotex, by the

selec-tion of a number from a menu, causes the dialing of

a prerecorded telephone number

auto-focus Also called automatic focus A process built

into some video cameras in which an impulse of

in-visible light is emitted to the subject and returned

to a pair of IR sensors This distance is then

calcu-lated by an IC Finally, a drive motor adjusts the lens

Hitachi, Toshiba and Akai were among the first

com-panies to feature auto-focus in their cameras Some

of today’s video cameras offer a more

sophisti-cated—and more accurate—auto-focus technique

Instead of relying on the not-too-precise IR

reflec-tion to measure distances, the focal adjustment of

these later cameras operates directly off the

image-sensing elements

auto-framing See Automatic framing.

automatic background control Automatic

bright-ness control

automatic backlight compensator Syn.: Backlight

switch

automatic backspace editing A VCR feature that

eliminates frame overlapping for glitch- and tion-free transitions A built-in microprocessor, afterchecking the signals of the control track, makes cer-tain that a new recording starts at the end of thelast frame each time a recording is begun from thePause mode

distor-automatic brightness control (ABC) 1 A TV receiver

circuit to keep the average brightness of the duced image essentially constant Its action is likethat of an automatic volume control in a sound re-ceiver Also called automatic background control

repro-2 In a TV receiver, a circuit that automatically justs the brightness of the display in accordance withthe level of ambient light near the receiver A pho-tocell may be used to measure the ambient light, itsoutput, after amplification, being used to controlthe grid bias of the picture tube

ad-automatic brightness limiter (ABL) A circuitry in TVs

to limit the maximum beam current to preventoverdriving the CRT

automatic channel scan A TV or VCR feature that

automatically programs the TV or VCR tuner memory

to lock in only active channels Usually operated fromthe remote control unit, the ACS, sometimes de-scribed as auto program, automatic channel search,

or programmable scan, searches up and down thosechannels active in a particular area and ignores theinactive ones that only bring in noise and static

automatic channel search Automatic channel scan automatic chapter search A videodisc player feature

that, when activated, takes the viewer to a lar selection on the disc This chapter search feature

particu-is often found on the remote control unit of a player

automatic chroma control Automatic color control.

automatic chroma correction See Automatic chroma

gain control.

automatic chroma gain control Automatic

correc-tion of chrominance channel gain typically usingsubcarrier burst level as a reference Syn.: ACC,automatic chroma correction

automatic chrominance control Automatic color

control

automatic color circuitry Electronic circuits built into

some TV sets, TV monitors and monitor/receiversdesigned to retain factory-preset color levels Auto-matic color circuitry locks in this balanced color ar-rangement regardless of discrepancies betweenchannels and scenes One disadvantage or criticism

of this feature concerns the viewer’s preference—the colors may appear too weak, too intense, toobluish, etc However, the color circuitry usually comeswith a switch that can be deactivated so that thecolors can be adjusted manually Also a techniciancan modify the automatic color circuitry so that itoperates more to the owner’s liking

automatic color circuitry

automatic color compensation A feature found on

some TV sets which monitors the three color guns

or electron beams so that the colors retain their

ac-curacy for the life of the CRT Under normal

condi-tions, tubes lose their color intensity as they age

With the addition of the special electronic circuitry,

the TV set can compensate for this imbalance

automatic color control (ACC) A circuit in a color TV

set to keep color intensity levels essentially constant

despite variations in the strength of the received color

signal Also called automatic chroma control and

automatic chrominance control

automatic color purifier Automatic degausser.

automatic color tint control See Color tint control.

automatic contrast control A circuit that maintains

the contrast of the TV picture at a constant average

level The manual contrast control determines the

average level and the automatic contrast control

maintains this average, despite variations in signal

strength as different stations are tuned in

automatic contrast correction A TV feature that helps

to bring out almost imperceptible detail in overly

bright or extremely dark sections of a screen image

automatic degausser An arrangement of

degauss-ing coils mounted around a color TV picture tube,

combined with a special circuit that energizes these

coils only while the set is warming up after being

turned on The coils demagnetize any parts of the

receiver that have been affected by the earth’s

mag-netic field or by the field of any nearby home

appli-ance Automatic degaussing permits a color TV

re-ceiver to be moved around a home without

read-justing purity controls Also called automatic color

purifier

automatic digital tracking A VCR feature that

auto-matically monitors its own playback Special circuitry

continually compares the RF signals on the

video-tape to reference signals in the circuit If the two

signals are not in sync, the special circuit emits a

correcting signal to the capstan servo, which

per-mits the video head to make adjustment for the best

possible signal

automatic fade control A video camera feature

de-signed to provide fade-outs at the end of scenes

and fade-ins at the openings When the fade

con-trol is engaged during the middle of a scene,

noth-ing occurs until the end, when the fade-out ends

the scene If the control is pressed before starting

the camera, the scene will open with a fade-in Some

cameras can be programmed to fade in and out on

a scene

automatic fine-tuning (AFT) control A circuit on such

units as VCRs and TV sets that keeps the frequency

of the oscillator in the tuner correct for best color

picture by compensating for drift and incorrect

tun-ing Eliminates the need for careful manual

fine-tun-ing each time a station is changed

automatic focus See Auto-focus.

automatic focus compensation A projection TV

fea-ture that adjusts for the disparity in projection ferences between the lens and the center of thescreen and the lens and the edges of the screen

dif-automatic focusing Electrostatic focusing in which

the focusing anode of a TV picture tube is internallyconnected through a resistor to the cathode so that

no external focusing voltage is required

automatic framing A video camera zoom lens

fea-ture that keeps the size of the subject constant.Whether the subject moves toward or away fromthe camera, the automatic framing function main-tains the original size of the image Canon was thefirst company to offer the special zoom lens fea-ture, also known as auto-framing, on some of itshigher-price 8mm camcorders

automatic frequency control (AFC) A circuit that

locks onto a chosen frequency and will not drift awayfrom that frequency; a technique to lock onto andtrack a desired frequency Used in TV transmitters,VCRs, and TV receivers to keep undesirable changes

to a minimum

automatic gain control (AGC) A control circuit that

automatically changes the gain (amplification) of asignal so the desired output signal remains essen-tially constant despite variations in input signalstrength In a camcorder, this feature is designed toincrease the signal only to the degree that the im-age gains an even intensity AGC increases a blanksignal to gray; in poorly lighted scenes it adds noise

to shadowed areas and produces less saturated ors Usually in the form of a switch, the AGC whenactivated has one disadvantage: some deteriorationoccurs in the video image In most VCRs a circuitcontrols the intensity of incoming audio and videosignals so that they match predetermined outputlevels while taping off the air or recording with acamcorder AGC is different from the sensitivityswitch that affects the general amplification of thevideo signal In audio, the AGC automatically boosts

col-or attenuates audio signals to optimum levels AGC

is also known as automatic level control, a featurefound on other instruments such as a color noisemeter, where it serves to stabilize input levels

automatic hue control A signal inserted into the

ver-tical blanking interval to help a TV set adjust theproper color Found on only a few TV models, auto-matic hue control, which is placed on line 18 of theblanking interval, may cause a problem when pre-recorded tapes encoded with the anti-piracy codeMacrovision are played The anti-piracy signal usesthis same line for its white pulses that are placedhere to defeat copying the tape information to an-other VCR Automatic hue control is similar in func-tion to automatic color circuitry

automatic image stabilization As applied to video

cameras, a method of achieving a steady recordedpicture while the user is walking with the video cam-

automatic color compensation

era Normally, the results of such camera recording

show up as images that are jumpy at best or

unin-telligible at worst The use of servo mechanisms and

rapidly responding compensating motors converts

camera movement into relatively smooth pictures

Modern video cameras do the stabilization

electroni-cally by using only a portion of the CCD array to

capture the image What portion of the CCD array

is used to capture the image is determined by the

amount and type of movement All this is

accom-plished by activating a special switch on cameras

equipped with automatic image stabilization

automatic iris control A camcorder feature designed

to automatically operate the lens opening by

“read-ing” the average light within a scene If the

auto-matic control cannot be overridden manually, then

there is no way to correct for extreme light or dark

backgrounds, etc Some cameras are equipped with

auto/manual aperture control, a more desirable

method, offering both flexibility and automation

automatic level control (ALC) When used to describe

an audio signal control, means the same as AGC

automatic light control (ALC) In video, an electronic

circuit that modifies any incoming light to a

prede-termined level In a vidicon camera, it is the control

that automatically adjusts the target voltage to

com-pensate for variations in light levels The ALC

af-fects light the way the AGC afaf-fects video

automatic lock A DVD player feature that holds the

optical assembly in place when the power is shut

off Similar to a “park” program for a computer disk

drive, the automatic lock helps to prevent damage

to the internal assembly whenever the machine has

to be moved

automatic pedestal control A process that

automati-cally adjusts the pedestal height in a received TV

signal as a function of input signal strength or some

other specified parameter

automatic phase control (APC) 1 A circuit in color

TV sets to reinsert a 3.58-MHz carrier signal with

exactly the correct phase and frequency by

synchro-nizing it with the transmitted color-burst signal 2

An automatic frequency-control circuit in which the

difference between two frequency sources is fed to

a phase detector that produces the required control

signal

automatic picture control A switch in some

color TVs to disable one or more of the regular

con-trols and use corresponding preset varlues Pushing

one button corrects for accidental misadjustment of

controls Sometimes also referred to as an automatic

gain control

automatic picture transmission (APT) A slow-scan

TV system in weather satellites; it is capable of

trans-mitting conventional TV pictures of clouds in the

daytime and IR pictures of clouds in at night Each

image is stored for about 200 seconds in a vidicon

while being scanned for transmission to earth

automatic program delay A professional/industrial

unit designed to provide delays from a few minutes

to several days, play back multiple feeds neously and accommodate incoming feed record-only sessions Delay actions are operated via timecodes, are frame-accurate and are affixed to the stu-dio reference clock Some units can handle a sched-ule of up to 1,000 events that can be programmedfor automatic operation

simulta-automatic program edit A feature, found mainly on

top-of-the-line laserdisc combination players, thataids in the process of dubbing from disc to tape.Once the user enters the length of tape selected forrecording, the player automatically calculates thenumber of tracks that can be recorded within thattime range

automatic programming A feature on VCRs designed

for presetting a number of programs on differentchannels and at various times to record automatically

automatic sag compensation Refers to a feature,

built into some test instruments such as color videonoise meters, that helps to produce uniform inputsignals

automatic scan tracking A feature, found on some

VCRs, designed to provide distortion-free slow

mo-tion from freeze frame to play mode See Visual scan.

automatic standard recognition (ASR) A circuit that

automatically selects the video standard of the ceived signal When TV reception is difficult, becausethe signals are weak, noisy, or badly distorted, thisfeature can be turned off and the video transmis-sion standard chosen manually

re-automatic switchover A feature that enables a

de-vice to accommodate either 110V or 220V tion without any manual adjustment

opera-automatic timing See Programmable timer.

automatic tint control A circuit in color TVs to

main-tain the correct flesh tones

automatic tracking A method of holding the video

head of a VCR on the track during playback ing adjustments are sometimes necessary to playback a tape recorded on a different machine

Track-automatic tracking reset A feature, found on some

older VCRs, that sets the tracking control to its fault setting each time a videotape is ejected or whenthe power is turned off Without this feature, theVCR owner must reset the tracking control manu-ally Otherwise, the next recording will permanently

de-be “off center,” a familiar problem with forgetfulVCR owners Automatic tracking reset differs fromauto tracking, which works completely automati-cally, requiring no adjustments

automatic transition editing A process that permits

glitch-free editing by automatically winding tape back a few frames when recording is stopped.When record is resumed, ATE aligns the beginning

video-of the new recording with the end video-of the previousone, thereby eliminating glitches and picture

automatic transition editing

breakup The problem with some types of ATE is

that the last part of the previous scene is sometimes

lost Also, exact editing is almost impossible JVC

was one of the first manufacturers to offer this

edit-ing technique found today on many VCRs and

por-table models Other VCR manufacturers use

differ-ent approaches, all of which achieve similar results—

almost glitch-free edits Sony, for example,

intro-duced its time-phase circuit When the tape restarts,

its movement is delayed electronically by special

cir-cuitry until the beginning of a field rather than the

middle of one ATE is also known as start,

edit-start control, scene transition stabilizing

automatic turn-on See auto cue and play.

automatic variable frequency scanning A feature

of display monitors that allows them receive a range

of signals that allows the user to switch from video

to computer graphics Some models can scan from

15 to 36 kHz while others offer more limited ranges

such as 31.5 and 35 kHz Several monitors designed

exclusively for computers call this feature

“multisync.”

automatic white balance A feature on camcorders

to help simplify white balance control By aiming

the camera at a white card or similar object and

pressing a button for a few seconds, a special circuit

in the camera scrutinizes and compares the RGB

channels and automatically corrects them

Some-times automatic white balance is only one, two, or

three controls used on a camera for color

adjust-ment Other cameras have improved the automatic

white balance adjustment by allowing it to be put

on hold By preventing the adjustment from

chang-ing automatically to match the shiftchang-ing light

condi-tions, the camera user can capture the dramatic

changes in such scenes as sunsets without the

cam-era compensating for these light changes

auto-phasing A video mixer with auto-phasing has

the ability to compensate for timing differences

be-tween the input sources, allowing it to perform

tran-sitions free of artifacts This is usually accomplished

by built-in line or frame synchronizers

auto-setup A type of professional/industrial TV

moni-tor that adjusts itself automatically, thereby

elimi-nating the fine tuning previously required by

tech-nicians These monitors are especially useful in

view-ing the same image when interchangview-ing videotapes

from one facility to another Another advantage is

the capture of the same image when several

auto-setup monitors, adjusted for the same color

tem-perature, are arranged in a row

autosizing 1 Syn.: Character sizing 2 In graphics

hardware, autosizing refers to a monitor’s ability to

accept signals at one resolution and display the

im-age at a different resolution Without autosizing,

an image must be adjusted manually so that it fills

the screen properly

autostereogram A technique used for 3D TV

with-out using special glasses for the viewer Large lensesare employed and the viewer must be in a very spe-cific, fixed location to watch the 3D picture It is notcompatible with normal TV programming

autostereoscopic system A 3D-image display

sys-tem that doesn’t require special glasses

auto-stop circuit A circuit that puts a VCR into stop

mode if any of the detectors that generate the stop operations sense a need to automatically stop

auto-the machine See Head drum rotation detector, Tape

end sensor, and Tape slack sensor.

autotiming The capability of some digital video

equip-ment to automatically adjust input video timing tomatch a reference video input Eliminates the needfor manual timing adjustments

auto-transition A transition (such as a mix or wipe)

that occurs without the use of a manual control,such as a fader arm Auto-transitions may be trig-gered from a button on the switcher, or externally

in the case of an editor (such as via a GPI interface)

In a DVE or vision mixer a “take” button (which may

be remote controlled) will usually trigger a predefinedtransition In this context, “take” is sometimes called

“auto-transition.”

auto-winder See Rewinder.

aux See Auxiliary bus.

auxiliary bus Some video mixers have extra switching

buses that allow video signals connected to theswitcher to be fed to external equipment such asdigital effects systems, slow-motion VTRs, etc Theauxiliary bus usually has no specific mixer function;

it is a utility feature Syn.: aux

auxiliary preset button A feature found on some

VCRs that is designed for setting in advance theoutput channel of a decoder that may be requiredfor some cable TV systems

auxiliary radio services, CATV Three auxiliary radio

services, Multipoint Distribution Service (MDS), tichannel Multipoint Distribution Service (MMDS),and Cable Television Relay Service (CARS), are used

Mul-to supplement and broaden the coverage of CATVsystems

auxiliary trigger A video camera option that provides

an additional pause button It can be useful in tain situations such as shooting in awkward or un-usual positions

cer-available light The amount of natural or artificial light

that is present Light is measured in lux or footcandlenumbers The lower the number, the greater thesensitivity of the camera

average picture level (APL) The average level of the

luminance within an active picture Usually expressed

as a percentage of reference white level APL is

of-ten incorrectly used instead of “flat field.”

average transmitted power In TV transmitting

sys-tems, a power depending on the picture content,being minimum for an all-white picture and maxi-mum for all black The NTSC/PAL composite video

automatic turn-on

waveform is inefficient in its power use, and most

of it is used for the sync and blanking pulses See

Rated transmitted power.

AVI Audio-video interleaving Microsoft® Video for

Windows file format for combining video and

au-dio into a single block in time, such as a video frame

ASF is intended to replace AVI

AVO Audiovisual object In MPEG-4, audiovisual

jects (also AV objects) are the individual media

ob-jects of a scene, such as video obob-jects, images, and

3D objects AVOs have a time dimension and a local

coordinate system for manipulating the AVO

AVSS Abbreviation for Audio-Video Support System.

A-weighted See Weighting noise.

axis Relating to digital picture manipulation, the x axis

is a horizontal line across the center of the screen,

the y axis is a vertical line, and the z axis is

perpen-dicular to plane of the x and y axes, indicating depth

and distance

axis of action See Line.

AYH option See HP 89400.

azimuth 1 The angle of the recording head in

rela-tion to the tape path To prevent crosstalk, or the

confusion of the video heads in playing back the

proper tracks that are crowded together, the head

gap angle is lifted slightly away from the

perpen-dicular In Beta format the tilt is 7 degrees Thus,

each of the two heads lays down a different pattern

on the tape It is as if one recording head placed

down a horizontal design within its diagonal track

while the second head recorded a vertical pattern

When the tape is played back, each head can

re-trieve only the design or pattern it recorded, thereby

eliminating crosstalk The azimuth system provides

a second advantage The tracks that the two heads

produce can be placed next to each other, ing the guardbands or spaces previously requiredbetween tracks This permits storing more informa-tion on the tape Sony first introduced the azimuthsystem in 1975 Some Super-VHS camcorders have

eliminat-a double-eliminat-azimuth 4-heeliminat-ad system theliminat-at reduces thesize of noise bars during the search mode and pro-vides noise-free still frames 2 A compass bearingexpressed in degrees of rotation CW from true north

It is one of the two coordinates (azimuth and tion) used to align a satellite antenna

eleva-azimuth blanking Automatic blanking of a radar

transmitter beam as the antenna scans a mined horizontal sector of its scanning region Thismay be used to prevent interference with TVs in acity close to the search radar site

predeter-azimuth-elevation (Az-El) mount An antenna mount

that tracks satellites by moving in two directions.The azimuth is the horizontal plane and elevation is

up from the horizon

azimuth error correction Electronic circuitry designed

to help correct artifacts in prerecorded Dolby round sound It helps with such problems as dia-logue, targeted for the front center channel, beingdirected to the rear speakers

sur-azimuth recording This recording is used in VHS to

eliminate the interference, or crosstalk, picked up

by a video head Since adjacent video tracks touch,

a video head can pick up some information fromthe adjacent track The azimuth of the head gapsassure that head “A” only gives an output whenscanning across a track made by head “A.” Head

“B,” therefore, only gives an output when scanningacross a track made by head “B.”

azimuth technique See Azimuth recording.

azimuth technique

b 1 Bit; for example, bps for bits per second 2

Bi-nary; for example, 1101b for the binary number

1101

B 1 Blue 2 CATV midband channel, 126-132 MHz.

3 See AAA rate 4 Byte 5 Baud 6 Bel 7 TV

standard; Australia, Austria, Denmark, Egypt,

Fin-land, Germany, Greece, Hong Kong, India, Iran,

Is-rael, Italy, Netherlands, New Zealand, Nigeria,

Norway, Pakistan, Portugal, Rhodesia, Saudi Arabia,

Singapore, Spain, Sweden, Switzerland, Turkey,

Yu-goslavia Characteristics: 625 lines/frame, 50 fields/

s, interlace—2:1, 25 fr/s, 15,625 lines/s, aspect

ra-tio—4:3, video band—5 MHz, RF band—7 MHz,

visual polarity—negative, sound modulation—F3,

pre-emphasis—50 us, deviation 50 kHz, gamma of

picture signal—0.5, used band—VHF

B channel A “bearer” channel is a fundamental

com-ponent of ISDN interfaces It carriers 64,000 bits/s

in either direction, is circuit switched and should be

able to carry either voice or data Can be used for

videophone (see Common intermediate format).

B&W Black-and-white.

b/s Bits per second.

B+ Supply voltage; the plus sign indicates the polarity.

B+ boost A circuit in TV sets that adds to, or boosts,

the basic B+ voltage The boost source is a

by-prod-uct of the horizontal deflection system See also

Damper.

baby 750-watt spotlight.

baby legs Low camera tripod.

back channel A means of communication from users

to content providers As content providers are

trans-mitting interactive television (analog or digital) to

users, users can also connect through a back

chan-nel to a Web site, for example The back chanchan-nel

can be used to provide feedback, purchase goods

and services, etc A simple type of back channel is

an Internet connection using a modem

back light Light placed behind objects in a scene and

pointing toward the camera to provide a rim of light,

that outlines the object and creates a sense of depth

by setting off that object from the rest of the scene

See Lighting.

back lot An area of a movie studio or TV station where

exterior scenes are shot

back matching The matching of the input and

out-put of electronic devices to reduce signal reflectionand ghosting Also known as impedance matching

back plate The electrode to which the stored charge

image of a camera tube is capacitively coupled Syn.:signal electrode Used in vidicon, iconoscope

back porch The area of the analog video waveform

between the end of horizontal sync and the start ofactive video In NTSC and PAL video signals, this part

is largely occupied by the color burst

back porch clamping The process of resetting video

signal level offset to zero by using the black level at

the back porch as a reference Syn.: clamping; black

level clamping

back porch switching Video signal switching

per-formed within the vertical blanking interval to mize the visibility of switching artifacts Syn.: verticalinterval switching

mini-back projection When the projection is placed

be-hind a screen (as it is in TV and various videoconferencing applications where the image is dis-played on a monitor or a fabric screen) it is described

as a back projection system In these systems theviewer sees the image via the transmission of light

as opposed to reflection used in front projection tems Audiences generally prefer back projectionsystems since they seem brighter

sys-back up In camcorders, an indicator on the menu

dis-play When the indicator appears, the settings areretained even when the battery is removed, as long

as the lithium battery is in place

back-back porch The portion of a back porch that

follows the color burst

background 1 Short form of the term color

back-ground—the same as matte generator 2 One ofthe video sources involved in keying Specifically, thebackground video is the video that has parts of itreplaced with the key fill, or foreground video Whenassociated with chroma-keying, for example in aweather report, the background is the weather mapand the foreground is the weather reporter

background color In videotex, the color of the area

of the character cell not occupied by the foregroundcolor; the color of the remaining area of the charac-ter The color may be any from the available color

tables or be transparent, in which case the full-screen

background color (or the cumulative result of all

pic-ture elements previously set or the video picpic-ture) is

seen

background generator Usually part of vision mixer.

The color and sometimes even the texture of the

generated background is adjusted with such

con-trols as “Luminance,” ”Chrominance,” ”Hue,” etc

Syn.: matte generator

background music jack An audio feature on some

camcorders that permits the user to connect an

ex-ternal sound source during the recording process

Adding background sound while the original

record-ing is in progress eliminates the usual generation

loss that is inherent in tape editing when music is

recorded after a recording session

background video See Background.

backing The plastic-ribbon base, usually mylar, onto

which is coated the oxide formulation of both

au-dio and video tape The backing is resistant to

stretch-ing and decomposition A binder to hold a coatstretch-ing

of magnetic oxide particles is placed on the

back-ing Backing is also called base film

backlight switch On some video cameras with

auto-matic iris control, a feature designed to provide one

f-stop more light In a scene containing a bright

background with a dark subject, the automatic iris

usually reads the darker part of the picture, causing

the main subject to be underexposed Activating the

backlight switch compensates for this by adding

more light Different from a contrast compensation

switch, the backlight switch only opens the lens

wider The backlight switch is sometimes listed as

an automatic backlight compensator

backspace edit A feature on many VCRs whereby the

tape will automatically rewind a certain number of

frames to create a clean cut when the camera is

reactivated

backspacing 1 Reverse cueing technique 2 A

fea-ture on VCRs designed to eliminate picfea-ture breakup

between scenes by backing up the tape when the

Pause mode is engaged Then when Record is

pressed, the tape begins at the end of the

previ-ously recorded section On some machines the tape

is backed up over the last few frames of the

previ-ous scene

backtiming 1 Reverse cueing technique for editing

backspace used in electronic editing 2 A technique

in live news, variety, or other programs in which the

last segment is rehearsed and timed Thus, in the

actual broadcast, as the time to begin this segment

approaches, the director is prepared to stretch it,

speed it up, or replace it In TV news programs,

backtime is the clock time (the actual time) at which

the last segment should begin if the program is to

end on time Thus, if the last segment is 40 s long

and the newscast must end at 11:28:55, the last

segment must begin at its backtime, 11:28:15 Each

of the preceding segments also can be backtimedfrom the end of the program working toward thebeginning

backward compatibility The capability of an improved

or enhanced piece of hardware to accept softwaredesigned for an earlier model For instance, S-VHSVCRs, that require special tape to benefit from theimproved features of the VCR, can play back stan-dard videotapes However, the conventionally re-corded tapes will not reflect the higher quality of

S-VHS VCR See also Compatibility.

Baer, Ralph Developed the first video games in 1971

while he was employed by Magnavox

Baird, John Logie Pioneer in British TV, inventor of the

first marketable home videodisc system in 1928 ing a TV system based on electro-mechanics (a light-sensitive cell and a mechanical revolving disc), he wasable to send a TV signal from London to New York in

Us-1928 The BBC employed his system when TV wasintroduced into England in 1929 Within a few yearsthe process succumbed to an all-electronic TV sys-tem developed in the USA by such scientists asVladimir Zvorykin and Philo T Farnsworth

balanced converter See Balun.

balanced modulator A modulator in which the

car-rier and modulating signal are introduced in such away that the output contains the two sidebandswithout carrier Used in color TV transmitters to ap-ply the I and Q signals to the subcarriers, as well as

in suppressed-carrier communications transmitters

balop Balopticon, an opaque projector made by Baush

and Lomb (hence the name) that casts positive ages by reflection for a TV camera The images gen-erally are artwork on a large slide (a balop) used asbackground for a TV or film scene or as part of asequence, such as a card or slide of a book jacket,product, name and address of a sponsor, or otheridentification

im-balun BAlanced to UNbalanced An adapter used for

converting 300 ohms into 75 ohms Usually suppliedwith a VCR to convert 300-ohm antenna wire, thebalun is often needed to connect a video game, VCR

or other component to a TV set, etc One example ofits function involves connecting a 300-ohm videogame to a 75-ohm projection TV system Also used

to balance the impedance of an outdoor antenna(usually 300 ohms) to the impedance of modern TVsets and VCRs (usually 75 ohms) There are two types

of baluns: a VHF-only and UHF/VHF model times called balanced converter, bazooka (slang), line-balance converter, and matching transformer

Some-balun coil A set of Some-balun coils are found between

antenna connection and TV tuner to match the put of 300 ohms to 75 ohms at the tuner input

in-banana tube A type of color picture tube in which

television signals were sent through a long, thin tube,followed by RGB signals flashed at timed intervals

band In audio/video, a span or range of frequency

band

signals Most TV sets and VCRs can be adjusted for

any one of three ranges: L (low band) for VHF

chan-nels 2-6; H (high band) for VHF chanchan-nels 7-13,

mid-band A-I and supermid-band J-W; and U for UHF channels

14-83 However, more sophisticated machines

of-fer four ranges: VHF low (channels 2-6), VHF

mid-high (channels 7-13 and cable A-I), UHF (14-83) and

VHF super (for superband channels on cable) TV

satellites work within two frequency ranges Large

dish antennas require the popular C-band, whereas

smaller dish antennas utilize the Ku-band

band separator An accessory that separates

incom-ing UHF, VHF and AM antenna signals so that they

can be directed to their respective terminals Some

band separators accept a 300-ohm (twin lead)

in-put while others take a 75-ohm inin-put and, with a

built-in matching transformer (75 to 300 ohms),

pro-vide a VHF output as well as a UHF output Band

separator is essentially a set of filters

band switch See Turret tuner.

banding A video defect in TV transmission in which

strips of the picture differ from adjacent areas,

of-ten due to a videotape player

bandpass filter A circuit that transmits alternating

currents whose frequencies are between given

up-per and lower cutoff values, while substantially

at-tenuating all frequencies outside this band Used in

TVs, VCRs These filters are also used in signal

pro-cessors to affect color and definition to allow only a

selected range of frequencies to pass through

band-stop filter A filter that attenuates alternating

currents whose frequencies are between given

up-per and lower cutoff values while transmitting

fre-quencies above and below this band It is the

opposite of a bandpass The band rejected is

gener-ally much wider than that suppressed by a trap Also

called band-rejection filter, bandstop filter, and

rejector circuit

bandwidth (BW) 1 Refers to the frequency range

transmitted by an analog system In video systems,

specifying the highest frequency value is sufficient,

since all video systems must transmit frequencies

down to 30 Hz or lower In transmission, the U.S

analog and digital SDTV channel width is 6 MHz 2

Incorrectly used as the equivalent of

information-carrying capability of digital TV systems, e.g “the

compression system has a 6-MHz bandwidth.” The

particular artifacts generated by such systems may

make nonsense of the quoted frequency

response

bandwidth compression A technique to reduce the

bandwidth needed to transmit a given amount of

information Bandwidth compression is used to

transmit voice, video and data

bandwidth efficiency In TV, the ratio of picture

qual-ity to RF bandwidth

bandwidth, HDTV (color set and color-difference set).

See SMPTE 240 standard.

bandwidth on demand Say you want two 56-Kbps

circuits right now for a videoconference Use one ofthe newer pieces of telecommunications equipmentand “dial up” the bandwidth you need An example

of such a piece of equipment is an inverse plexer Uses for bandwidth on demand include videoconferencing, LAN interconnection and disaster re-covery Bandwidth on demand is typically only fordigital circuits and it’s typically carved out via a T-1permanently connected from a customer’s premises

multi-to a long distance carrier’s central office, also called

a POP—Point of Presence

bandwidth reduction, EUREKA-95 HDMAC system

To transmit the 21-MHz luminance baseband patibly to the D-MAC and D2-MAC receivers, band-width reduction by a factor of approximately four isrequired This is accomplished by the coding anddecoding process as follows The encoder has

com-“branches” for three degrees of motion: an 80-ms(4 fields) branch for stationary and slowly movingareas of the scene; a 40-ms (2 fields) branch formoving areas; and a 20-ms (1 field) branch for rapidmotion and sudden scene changes These branchesare switched to the transmission channel by themotion processor The switching signals are alsotransmitted to the receiver via DATV channel, wherethe branch in use at a particular time, after decod-ing, is connected to the receiver for processing anddisplay at the 1250/50/2:1/16:9 rates of the camera

or telecine equipment at the transmitter

The chrominance signals, each of 10.5 MHz band, are transmitted after similar 3-branch encod-ing, but without motion compensation The encoding

base-in the 80-ms branch extends over four fields Hence,the luminance bandwidth for stationary areas is re-duced from 21 MHz to 5.25 MHz But the 40-ms and20-ms branches extend only over two fields and onefield, respectively, so additional bandwidth reduction

is required This is achieved by several processes, e.g.,

“quincunx” scanning (scanning of successive pictureelements alternately from two adjacent lines) on al-ternate fields, which produces a synthetic interlace;and line shuffling that interleaves high-definitionsamples so that two lines within a field are transmit-ted as one MAC/packet line, to which the D-MACand D2-MAC receivers respond compatibly The cluesrequired to perform the inverse operations at the re-ceiver are transmitted over the DATV channel

bandwidth requirements The bandwidth required

by a TV signal is half the number of pixels ted per second A wide bandwidth is required toresolve fine detail while maintaining a high enoughpicture repetition rate to avoid objectionable flicker.This explains the huge spectrum requirements of TVsystems

transmit-Bandwidth Segmented Orthogonal Frequency Division Multiplexing BST-OFDM attempts to im-

prove on COFDM by modulating some OFDM

car-band separator

riers differently from others within the same

multi-plex A given transmission channel may therefore

be “segmented,” with different segments

being modulated differently

bank 1 A set of similar devices connected together

for use as a single device (bank of resistors) 2 A

storage area (data bank) 3 In film and TV, rows of

lighting 4 In broadcasting, a pool or collection of

commercials (commercial bank)

bank timer A VCR timer-related feature that can store

several sets of timer-recording instructions under

different categories On-screen menus help the

viewer to code in timing information under such

topics as news, cinema, cartoons and drama These

instructions are then entered into the timer section

for upcoming recordings

bar A common test pattern component The bar looks

on a TV screen as a vertical strip, usually specified by

color, level and edge rise-time, e.g 75% 2T White

Bar Sometimes the bar component is called

“win-dows” or ”box.”

bar code A pattern of vertical lines of differing widths.

These can be read by a bar-code scanner to provide

data to a VCR See also LCD digital scanner

pro-gramming system.

bar code programming A VCR feature that

simpli-fies transmitting recording instructions to the clock/

timer of the VCR VCRs that come equipped with

this programming function provide a pen-like

de-vice, called a bar-code scanner, and a programming

card containing a list of days, time segments and

channel numbers The owner, using the scanner,

sim-ply checks off the appropriate day, time and

chan-nel on the card for each program to be recorded

The information is then transferred to the VCR to

be displayed for confirmation on the TV screen

bar generator A signal generator that delivers pulses

uniformly spaced in time and synchronized to

pro-duce a stationary bar pattern on a TV screen A

color-bar generator produces these color-bars in different colors

on the screen of a color TV set

bar pattern The pattern of repeating color bars

pro-duced by a bar generator, for adjusting color TV

receivers

barrier grid See stabilizing mesh.

bar tilt Time domain parameter indirectly showing

low-frequency response distortion by checking bar

wave-form The tilt of the flat top of the bar is usually

expressed as a percentage of the bar’s amplitude,

ignoring overshoots Syn.: tilt

bar-code scanner An optical character reader that

can automatically read data from documents

bear-ing information formed with a special bar code See

also LCD digital scanner programming system.

barker audio See Video inversion.

barker channel A channel to advertise the pay TV

service to nonpaying would-be viewers The main

audio channel can be used as a barker channel

Barkhausen A term applied to a display of one or two

black vertical lines on the left side of the TV picturetube due to some spurious behavior (oscillation) inthe circuit These lines are usually seen best whenthere is no picture on the screen (just a blank raster)

Barkhausen magnet A permanent magnet mounted

on the horizontal output tube of a TV receiver to

reduce Barkhausen oscillations.

Barkhausen oscillation An undesired oscillation in

the horizontal output tube of a TV receiver; it causesone or more ragged dark vertical lines on the leftside of the picture

barn doors Adjustable flaps that fit over a video light

to concentrate the beam in a broad or narrow path.Also called flippers

barracuda British TV and film slang for a telescopic

light support, made from lengths of metal pole

barrel distortion 1 The characteristic distortion of a

scene by a wide-angle lens: a rounded and proportion look around the edges of the scene,caused by objects being too close to the lens 2.Distortion in which all four sides of a received TV

out-of-picture bulge outward, like a barrel See Distortion.

barrel effect Vertical edge distortion of a screen

im-age The effect tends to be more pronounced in rearprojection TV systems

barrier display section In (2+3)D-image display

sys-tem with parallax barriers, a section in which thenumber of parallax barriers, width aperture ratio,shape including the interval, and generating posi-tion can be freely programmably controlled inaccordance with an instructed input

barrifocal mirror system One of the 3D-image

dis-play systems that doesn’t require special glasses

bars and red Popular two-part test pattern with

stan-dard color bars above red field Useful for the tection of noise and moire Professional jargonsometimes refers to this signal as “Bars in Blood”!Syn.: split field/red

de-base The part of an electron tube that has the pins,

leads, or other terminals to which external tions are made either directly or through a socket

connec-base film Backing.

base light The general illumination of an area The

base light helps provide the camcorder with a ing level above that which is needed to prevent elec-tronic noise All video units, such as VCRs andcameras, produce video noise that affects the videosignal The base light, which is usually located overthe subject, helps to overcome this

light-baseband 1 The band of frequencies containing the

information, prior to modulation (and subsequent

to demodulation) The band that transmits pictureand synchronizing signals in TV; the band contain-ing all the modulated subcarriers in a carrier system.When applied to audio and video, baseband means

an audio or video signal that is not RF modulated(to channel 3 or 4 for example) 2 In satellite TV,

baseband

the raw audio and video signals prior to modulation

and broadcasting Most satellite headend equipment

utilizes baseband inputs More exactly, the

compos-ite unclamped, non-de-emphasized and unfiltered

receiver output This signal contains the complete

set of FM modulated audio and data subcarriers

baseband signaling The transmission of a digital

sig-nal without modulation Only one sigsig-nal at a time

can be present on a baseband channel

baseband transmission A type of data transmission

in which each medium carries only one signal, or

channel, at a time

baseband video Same as composite video (CVS or

CVBS)

baseline sequential JPEG The most popular of the

JPEG modes that employs the lossy DCT (Discrete

Cosine Transform) to compress image data as well as

lossless processes based on variations of DPCM

(Dif-ferential Pulse Code Modulation) The “baseline”

sys-tem represents a minimum capability that must be

present in all Sequential JPEG decoder systems In this

mode, image components are compressed either

in-dividually or in groups A single scan pass completely

codes a component or group of components

basic cable A term referring to the minimum services

a U.S subscriber of a CATV system gets for the

mini-mum monthly charge These services usually include

VHF and UHF channels, CNN, religious and weather

channels and other programming nationally

distrib-uted Other services, like HBO, require additional

monthly fees

basic rate interface (BRI) There are two “interfaces”

in ISDN: BRI and PRI In BRI, you get two bearer

B-channels at 64 kilobits/s and a data D-channel at 16

kilobits/s The bearer B-channels are designed for

PCM voice, video conferencing, group four facsimile

machines, or whatever you can squeeze into 64,000

bits/s full duplex The data D-channel is for bringing

in information about incoming calls and taking out

information about outgoing calls It is also for

ac-cess to slow-speed data networks, like videotex,

packet switched networks, etc One BRI standard is

the “U” interface, which uses two wires Another

BRI standard is the “T” interface, using four wires

basic set A film, TV, or stage set with furniture and

scenery but without props

basic television service A charge for delivery of TV

broadcast by cable; typically a monthly fee for the

lowest level of service

basket Cassette lift mechanism in front-loading VCRs.

Also called elevator

bat blacks In video, to fade out; to turn a picture to

darkness or superimpose over a picture

battery See Lead acid battery, Nickel cadmium

battery.

baud (B) A unit used to measure the number of times/

s that a data transmission channel changes state

Since, even in a binary channel, the baud rate

in-cludes all elements transmitted including tion elements, the baud rate is not necessarily equiva-lent to the data rate, and baud is not necessarilysynonymous with bits/s

coordina-bazooka Slang for a large item Slang term for balun.

BB 1 Black burst 2 CATV hyperband channel,

306-312 MHz See TV channel assignments.

BBC [color] bars Color bars with the nomenclature

100/0/100/25 in 625/50/2:1 scanning standard

BBC standard The British Broadcasting Company in

London began transmissions in 1929, but their firstservice was more or less experimental even thoughthe public was “invited” to buy receivers It was anelectromechanical system with a picture resolution

of 30 lines and a field rate of 25 Hz Then, in 1936,

an all-electronic system was adopted and the dard was set at 405 lines/50 Hz, which has remained

stan-in effect sstan-ince then as the standard for VHF blackand white TV in England

BCU A big close-up of a picture in photography, film,

or TV; ECU is an extreme close-up

BDC Block Downconversion.

beam 1 A semi-coherent flow of electrons 2 A

nar-row stream of essentially unidirectional netic radiation (as in a radio wave) or chargedparticles (as in an electron beam)

electromag-beam adjustment A control on vidicon cameras that

regulates the amount of current flowing in the beam

beam angle See Cathode-ray tube.

beam bender Ion-trap magnet See Ion trap.

beam bending Deflection of the scanning beam by

the electrostatic field of the charges stored on thetarget of a camera tube

beam blanking Blanking.

beam convergence The adjustment that makes the

three electron beams of a 3-gun color picture tubemeet or cross at a shadow-mask hole

beam current The current of a scanning beam in

camera or TV CRTs

beam deflection tube A color picture tube with a

single electron gun and in which the screen is posed of horizontal stripes of red, green and bluephosphors arranged in sequence A grid of horizon-tal wires is mounted close to the screen and, by ap-plying suitable potentials to these wires the electronbeam can be deflected so as to strike the phosphorstripe giving the required color Also called beam-switching tube

com-beam indexing Refers to a signal generated by an

electron beam that is deflected and fed back to acontrol device Beam indexing is one of several meth-ods of presenting images upon a screen

beam landing errors Errors that can occur when the

electron beam does not strike the target correctly,owing to distortions of the magnetic fields This mayhappen in cameras and TV CRTs in areas where twofields interact, such as line and frame deflectingfields

baseband signaling

beam magnet Convergence magnet.

beam splitting Method of dividing the color

compo-nents of the image so they can be cast upon more

than one vidicon target area (or tube); used in 2-,

3-and 4-tube color cameras

beam-indexing tube A color TV picture tube with a

single electron gun and in which the screen is

com-posed of vertical stripes of red, green and blue

phos-phors arranged in sequence A beam indexing system

operated, e.g., by signals from vertical stripes

inter-leaved with the red, green and blue groups ensures

that at any instant the electron gun is always

switched to the phosphor stripe on which the beam

is incident

beam-splitting systems Devices for splitting a light

beam to form two or more separate images from a

single lens Often used in color TV cameras to form

the three primary color images Beam-splitting can

be accomplished by prisms, semi-reflecting surfaces

and dichroic mirrors

beam-switching tube Beam deflection tube.

beamwidth The acceptance angle of an antenna,

usu-ally measured between half-power (3 dB) points

bearding A video distortion appearing as short black

lines to the right of bright objects It’s caused by

interruptions in the horizontal sync of the tape

Beck, Stephen Video artist, electronic engineer

Work-ing with a video synthesizer, he originated the

con-cept of combining color, form, texture and motion

to produce abstract kinetic video art His works are

recognized worldwide In the early 1970s he worked

on a PBS series called “Video Visionaries.”

beeper feedback See Audio alarm, Trigger alarm.

bel Symbol: B A relative measurement, equal to the

logarithm to the base 10 of the ratio of two amounts

of power One power value is a reference value The

decibel, a smaller unit equal to 1/10 B, is more

com-monly used

bell filter Filter in a SECAM decoder to

empha-size the chrominance signal prior to frequency

de-modulation

bells and whistles Special effects, flashy graphics,

and other extras added to films, TV programs, or

any audiovisual presentation

below the line Technical and production costs as

in-dicated in the program budget—includes

produc-tion equipment and technical personnel

BER (or B.E.R.) Bit Error Rate Accuracy of digital

de-modulation or decoding Analogous to SNR, but

re-fers to digital transmission

best time available (BTA) An instruction with a

pur-chase order for a TV or radio station to broadcast a

commercial at the most favorable time available

Beta format A system of home videotaping using a

special 2-hub plastic videocassette, 1/2-inch tape and

recording speeds incompatible with other formats

Introduced for home use in 1975 by Sony, the Beta

format uses a cassette smaller than that of its

com-petitor, the VHS format Although the originator ofhome VCR, Beta has almost completely disappeared

in the U.S Other companies, including Zenith,Toshiba, Marantz and Sanyo, had originally selectedthe Beta format for their VCRs and video cameras,but have since abandoned that format in favor ofthe more successful VHS

Beta hi-fi A full-frequency stereo process for VCRs

developed by Sony in 1982 Conventional video reo as found on VHS machines uses longitudinalsound tracks (tape passing across a stationary head),but this method produces poor sound quality be-cause of two factors The tape speed of video ma-chines is very slow, only a fraction of that of audiorecorders Secondly, the small space of the tape al-lotted to the normal mono audio track has to besplit in half to provide for the dual channels neces-sary for stereo For these reasons, a noise reductionsystem such as Dolby B is required to improve some

ste-of the less-than-adequate sound Sony avoided thesetwo shortcomings by using the video heads to placethe FM-modulated audio (AFM — Audio FM) sig-nals onto the tape, superimposing the channels overthe video signal A greater dynamic range results,with a frequency response said to be from approxi-mately 20-20,000 Hz The portion of the tape oth-erwise assigned to the audio signal can still be usedfor a mono sound track (to keep the system com-patible with other Beta machines) It can also be used

as a third audio track for different functions, such

as recording a foreign language

Betacam Sony’s trade name for component analog

tape recording format The term is often incorrectlyassociated with component analog video interfac-ing in general The system has continued to be de-veloped over the years, offering models for theprofessional/industrial markets Digital versions alsoexist as the high-end Digital Betacam and Betacam

SX for ENG and similar applications

Betacam color bars Historically these bars followed

early Betacam signal levels, giving rise to 75% colorbars in YPrPb format with PrPb gain boosted by afactor 1.333 At the righthand side of the pattern,the “black set” test and 100% white bar are added

In the 625 version the white level is 700 mV, in the

525 version the white level is 100 IRE (714.825 mV)

Betacam SP The Sony trademarked “Superior

Perfor-mance” analog component video tape recording

format similar to the Betacam format Betacam SP

players will play back Betacam recordings but notvice-versa Betacam SP is recorded on oxide or metaltape

Betacam-SX Sony’s trademark for a component

digi-tal tape recording format with signal compression.Developed for news acquisition Compression is simi-lar to MPEG-2, but with fixed GOP structure to al-low easier edits The digital signal recorded on tapeuses a higher level of digital compression (DCT-based)

Betacam-SX

than Digital Betacam, which results in a lower

bit-rate after coding At the interface level it is

compat-ible with D-1 format, i.e conforms to ITU-R BT.656

Betacam-SX players can play back analog

compo-nent Betacam SP tapes

Betamax Sony’s trade name for its initially popular

1/2-inch Beta format VCR The first Betamax, the

SL-7200, was introduced in 1975 The Betamax has

virtually disappeared in the U.S., losing marketshare

to the VHS format

Betascan Sony-developed feature found on Beta VCRs

that allows for quick picture search (15x, Beta III)

Betaskipscan Sony Betamax feature that provides

in-stant switching from high-speed FF or REW mode

to Betascan search mode to determine location on

the tape

bezel In video, the frame surrounding a video picture

that has different proportions from that of the TV

screen For example, when some cable or broadcast

stations present a wide-screen theatrical film in its

correct aspect ratio (about 16:9), the top and

bot-tom portions of the screen (4:3 aspect ratio) remain

blank Some local and network stations provide a

decorative bezel to replace the normally black

por-tions of the screen Bezels may come in different

proportions

BF Burst flag.

B frames Bi-directional predictive frames used by

MPEG These are composed by assessing the

differ-ence between the previous and the next frames in a

television picture sequence As they contain only

pre-dictive information, they do not make up a

com-plete picture and so have the advantage of taking

up much less data than the I frames However, to

see the original picture requires a whole sequence

of MPEG pictures to be decoded See MPEG.

BG Burst flag.

bias light Internal illumination of a TV camera tube

that reduces or removes the halo (reflected light that

extends beyond the desired boundaries)

biased automatic gain control Syn.: delayed AGC.

It is a process that comes into operation only for

signals above a predetermined level

bible In the production of a TV series, the general

out-line of plots and character development prepared

before the first program of the season Some

pro-ducers refuse to bible the show, in order to

main-tain the flexibility to make plot and cast changes

during the season

biconcave A lens configuration in which the lens

ele-ment has an inward curve on both sides

biconvex A lens configuration in which the lens

ele-ment has an outward curve on both sides A

magni-fying glass is the most common example of a

biconvex lens

bicycling The shipment of videotape recordings of TV

programs from one transmitting entity to another

In order to save film and videotape costs, the

pro-grams are sent to a station or cable system whenthey are needed for the station’s schedule After aprogram is broadcast, that station or system sends

it on to the next operation

bidirectional Describes a microphone that accepts

sound waves from two different directions, whileattenuating sound waves from any other direction

bifilar transformer A transformer in which wires for

the two windings are wound side by side to giveextremely tight coupling When used as TV IF trans-formers to couple stagger-tuned IF stages, the highcoupling eliminates the need for a DC blockingcapacitor

BIFS Binary format for scenes In MPEG-4, a set of

elements called nodes that describe the layout of amultimedia layout BIFS-Update streams update thescene in time, BIFS-Anim streams animate the stream

in time BIFS are organized in a tree-lined cal scene graph node structure derived from VRML

hierarchi-Bildschirmtext (Btx, BTX) Now called Datex-J The

public videotex system in the Federal Republic ofGermany

billy- A prefix denoting one thousand million,

synony-mous with “giga.”

binary gradation A gradation of black and white binary pair Synonymous with bistable circuit binary variable A variable that can have one of two

values (0 or 1) Also known as two-valued variable

binary-coded character A character represented by

a binary code

binder A chemical adhesive to hold the magnetic

ox-ide particles to the backing or base of the vox-ideo-tape The quality of the binder is important in thatits composition determines the number of dropoutsthat are likely to occur

video-bipolar PG In VCRs, pulse generator signals that have

both positive and negative excursions

bipolar sync See Tri-level sync.

bird Jargon or nickname for communications satellites birdseye In film and TV, a spotlight with a reflector

back invented by Clarence Birdseye (1886-1956),who is better known for developing methods forquick-freezing foods

B-ISDN Broadband ISDN See ISDN.

bistable Having two states.

bistable circuit A circuit that can be triggered to adopt

one of two stable states Also known as binary pair,bistable trigger circuit, trigger pair

bistable trigger circuit Syn.: bistable circuit bit A single binary information unit Usually represented

by “0” or ”1.” As a jargon term can be used todescribe a single step of the quantization scale

bit assignment In video compression, the process of

creating the compressed data bit stream from theraw output of the compression algorithm

bit bucket Any device able to store digital data—

whether it be video, audio or other types of data

bit budget The total number of bits available on the

Betamax

media being used In DVD, the bit budget of a

single-sided/single-layer DVD5 disk is 4.7 GB

bit depth The number of levels that a pixel might have,

such as 256 with an 8-bit depth or 1,024 with a

10-bit depth

bitmap A digital representation of an image in which

the bit-mapped characters, composed of dots or

pixels, are readable on a screen

bit parallel format See Parallel digital [video]

inter-face format.

bit pattern A sequence of bits Bit patterns may be

used to represent characters in a binary code

bit plane In digital video, with display hardware that

has more than one video memory array

contribut-ing to the displayed image in real time, each memory

array is called an image plane However, if the

ar-rays have only one bit-per-pixel, they may be called

bit planes

bit rate Relating to the speed of a device, e.g., the

speed with which binary digits can be transferred

over a communications channel May be measured

in bits/s or baud It is the digital equivalent of

band-width

bit rate conversion See Sampling rate conversion.

bit serial format Format where 10-bit serialized video

data are transmitted via BNC type connector or

fiber-optical connector with clock rate: 10 x 4 x 3.579 =

143 MHz (digital composite NTSC and PAL-M), 10 x

4 x 4.433 = 177 MHz (digital composite PAL), 10 x 27

= 270 MHz (digital component 4:2:2) or 10 x 36 =

360 MHz (ITU-R BT.601, digital component) Syn.:

Serial Digital [Video] Interface

bit stream A serial sequence of bits.

BitBlt Abbreviation for bit boundary block transfer, a

data transfer function that moves a rectangular

re-gion of pixels within or between bitmaps This

func-tion often is used for displaying pop-up windows,

cursors, and small symbols such as text BitBlt

tradi-tionally is capable of performing a Boolean (e.g.,

XOR) operation between the source and

destina-tion during the transfer Also called RasterOp

BITC Burned-In Time Code This means the time code

information is displayed within a portion of the

pic-ture, and may be viewed on any monitor or TV

bite A short segment, or take, that is repeated on

net-work radio and TV news programs

bitmap A region of memory or storage that contains

the pixels representing an image arranged in the

sequence in which they are normally scanned to

dis-play the image If a bitmap can be directly disdis-played

on the screen, it is referred to as a frame buffer If

the bitmap cannot be viewed directly, then its data

must be moved to display memory to be viewed

For example, a text font can be stored in an

off-screen bitmap, and each character is moved to the

proper place on the screen (using BitBlt) as it is

needed

bitmap descriptor In the DVI runtime software, a data

structure that contains the parameters of a bitmapincluding its location in memory, its dimensions, andits pixel format

bitmap font A special format of a text font that

con-tains pixel values for each text character

bitmapping A technique used in graphics display in

which the information displayed on a screen sponds, pixel by pixel, with bits held in memory

corre-bits per pixel (bpp) The number of corre-bits used to

repre-sent the color value of each pixel in a digitizedimage

bits per second The number of bits transmitted per

second over a communications line

BK Black.

BL Black; also blue, depending on the context, so when

in doubt, spell it out

blab-off-switch British slang for a remote-control

de-vice to mute the sound of a TV program, such asduring the commercials

black Very dark Pitch black or pure black means

to-tally without light Television black reflects a verysmall amount of light from the screen, about 3%reflectance

black after white A TV receiver defect in which an

unnatural black line follows the right-hand contour

of any white object on the picture screen The samedefect also causes a white line to follow a suddenchange from black to a lighter background It iscaused by receiver misalignment

black and white signal 1 A signal wave that

con-trols luminance values in black and white TV 2 Theportion of a signal wave that has major control ofthe luminance values in a color TV system, regard-less of whether the picture is displayed in color or inblack and white

black and white television Television that reproduces

a picture in black and white (b&w) with shades ofgray between black and white Black and white re-ceivers use the brightness information transmitted

as part of the color signal—the luminance signal—but the image is produced in black and white

black and white transmission Transmission of a

sig-nal wave that controls the luminance values in a TVpicture but not the chromaticity values The result is

a black and white picture

black body A perfect absorber of all incident radiant

energy It radiates energy solely as a function of itstemperature

black body radiator See Full radiator.

black box 1 An electronic device with known

perfor-mance characteristics but unknown constituents 2

A general term given to a variety of electronic devicesbecause of their color and shape They include imageenhancers, image stabilizers, video amps and up con-verters that can be connected to a VCR or a TV set

black burst (BB) A video signal that contains the color

black This gives the signal the major reference points

of color-burst pulse, a black reference, and sync It is

black burst

used as a base “neutral” signal to format tape and to

reference most video hardware Black burst tells the

video equipment the vertical sync, horizontal sync,

and the chroma burst timing Syn.: house sync

black-burst generator See black burst.

black clipper See Black limiter.

black clipping A video control circuit that regulates

and contains the black level of the video signal so

that it does not disturb or appear in the sync

por-tion of the signal

black compression A reduction in TV picture-signal

gain at levels corresponding to dark areas in a

pic-ture The effect reduces contrast in the dark areas

of the picture as seen on monitors and receivers

Also called black saturation

black crushing Compression of low values of signal

(i.e., black) resulting in loss of significant detail in

the darker picture areas

black current stabilizer An adjustment on each CRT

gun (R, G, B) for setting the leakage current when

the gun is in the vertical blanking interval If not

adjusted there will be background discoloring The

leakage is measured via sensing resistors in the CRT

cathode circuits

Black Entertainment TV A CATV channel targeted

for a black audience and offering entertainment,

sports and films BET also covers interviews and other

news pertaining chiefly to its black audience

blacker-than-black 1 Excursion of the TV video

waveform signal downwards below the nominal

black level; e.g., the excursion of the

synchroniz-ing pulses to zero signal 2 The amplitude area of

the composite video signal below the reference

black level in the direction of the synchronizing

pulses (e.g., the luminance signal overshoots after

a white-to-black transition) ITU-R BT.601

quanti-zation scale provides 15 levels of headroom below

reference black to allow some blacker-than-black

throughput

blacker-than-black region The portion of the

stan-dard TV signal in which the electron beam of the

picture tube is cut off and synchronizing signals are

transmitted These synchronizing signals have greater

peak power than those for the blackest portions of

the picture

black filter A filter, used in devices for direct display of

an image on the retina of the eye using a scanning

laser, that attenuates the intensity of the incident

laser beam to such a level that laser beam will not be

harmful to an eye into which it is introduced

black level The bottom level of the picture signal,

be-low which are the sync, blanking, and other control

signals that do not appear as picture information

This level is generally set at 75% of the maximum

signal amplitude of the synchronizing pulses and

represents the darkest an image can get It defines

what black is for the particular video system If for

some reason the video dips below this level, it is

referred to as blacker-than-black You could say thatsync is blacker-than-black

black level clamp Circuit that establishes the signal

level corresponding to black at a finite level sary after AC coupling to restore the DC compo-nent in the TV signal, and to eliminate low-frequencydistortion and hum The signal is fed through a ca-pacitor and shorted to a fixed direct voltage duringline blanking intervals Used also in line clamp am-plifiers

Neces-black level clamping The process of resetting video

signal level offset to zero by using the black level at

the video back porch as a reference Syn.: back porch

clamping; clamping

black level control A feature on some TV sets that

controls the extent of black within picture areas Thismay affect the contrast of the image, but it is notstrictly a contrast control; it does not determinewhich portions of the image should turn black butrather the degree of blackness The conventionalcontrast control, on the other hand, constricts orextends the range of contrast only On broadcast-studio quality video cameras the black level controlfeature is called “pedestal” while the contrast con-trol is known as gain

black level noise Very similar to a white spot noise

spike except it is in the opposite or black level tion

direc-black level retention The ability of a TV set, VCR or

similar unit to reproduce black areas on a TV screen.Although no TV receiver produces an absolute black,manufacturers have constantly experimented in thisarea to improve the overall image contrast The range

of color contrasts depends on the span between thedarkest gray and purest white The wider the range,the more noticeable the distinctions between hues.This variation in shades helps to give the appearance

of depth or three dimensions to the image on the TVscreen The contributions over the years of severalcompanies, including NEC, Proton, Zenith, Sony andPanasonic, have resulted in subtle improvements inblack level retention These enhancements are moreprominent in the higher-priced TV monitor/receiversthan in low-end TV sets Black level retention is mea-sured by percentage; e.g., 80% or better is rated sat-isfactory while 90% is considered good

black limiter A device preventing a video signal being

lower than some pre-set threshold near black level.Syn.: black clipper

black matrix Picture tube in which the color

phos-phors are surrounded by black for increasedcontrast

black matrix lenticular screen See Black stripe

pro-jection television.

black matrix/black surround A technique to reduce

the unexcited field brightness and the light reflected

by the phosphors of color kinescopes The resultscan be seen by observing the kinescope of a color

black-burst generator